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What causes these "anti-microclimates"?


Pee Dee Palms

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Recently I was looking at some USDA hardiness zone maps for Texas, Louisiana, and Mississippi and noticed something off about three different towns. These three towns that I have posted pictures of all seem to have a lower hardiness zone than the surrounding area which I would think should be the opposite. I thought that the asphalt and heat the buildings and roads create could potentially bump the hardiness zone up half a zone like most large cities. Why would these three towns be half a zone below the surrounding area?

The three towns in question are: Pearsall, TX - Baton Rouge, LA - Vicksburg, MS

pearsallhardinesszone.png.5bf25c92aba419e644469a99ae09735e.png


batonrougehardinesszone.png.e917b07731f2ff87be2a0cc8b634cb61.png

 

vicksburghardinesszone.png.4580cff13f133cedb976760068fd7091.png

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I bet it has to do with elevations.  Like low areas surround by higher ground where cold air funnels in and sits.  It could also be high elevation, temps drop the higher you go.

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They are not "anti-microclimates." They are examples of the poor quality of these maps created at great cost and with much fanfare by the "PRISM" group in Oregon...but went across like a lead balloon to anyone who tracks weather/climate. It was announced during the many years of their development that these would take into account local variations with incredible detail, etc. and, sadly, that just isn't reflected in the maps. Even small urbanized areas can create a marked difference in microclimate. I used to live in Natchez, Mississippi, in the downtown grid just a few blocks from the bluff overlooking the Mississippi River. The downtown area, except for a couple of air-drained cold-spots (mostly creeks/gullies/"bayous"), is a zone 9a, while the surrounding countryside is mostly 8b or even colder (I had a Davis weather station as did/do several others there, and tracked the data for years). One of the problems is that NOAA often uses airports as defining weather stations for metro areas. The Natchez airport is located north of town on a grassy plain more inland from the river, and is markedly colder than the downtown area.

The maps also don't seem to take local geography and air-drainage into account. One example that I regularly experienced when driving back and forth from Baton Rouge to Natchez was the journey up and down the Homochitto Ridge, about 20 miles south of Natchez. On a cold, still, clear night, you could leave Woodville (a town to the south of the ridge) and, while driving up and over that ridge near the settlement called Doloroso, the car-thermometer would climb roughly 10 degrees; and back down as one traversed on down the other side into the Homochitto River basin. Yet this is not reflected on this map. I know there are many more examples of this (and of course this and any other warm slopes or frost-pocket/river-course low spots could have easily been modeled/generated with a desktop computer using USGS topo data).

Likewise, Baton Rouge, which is a fairly large, sprawling city nowadays, does have a warmer microclimate than the surrounding area. This is especially marked in the downtown/Government St. and Garden District areas. In the latter, there are large numbers of Live Oaks sheltering the streets and homes, adding several additional degrees to the Urban Heat Island. Also, many areas of Louisiana have large bodies of water, sometimes lakes, sometimes rivers, sometimes just boggy, swampy zones that aren't readily visible on maps. And it is in general a quite rural (or small town) area, and that makes it tricky to estimate just how the microclimates come and go. (There are some South Louisiana folks here on this forum who could elaborate on that, I'm sure.) And again, the Baton Rouge Airport is located north of town in a somewhat colder area (and temps there would usually track within a degree or two of the Natchez downtown grid, despite being 75 miles south of Natchez). So I would assume they relied on the airport readings to either define or bias the zone definition for the city of Baton Rouge.

I can't speak to the issue of Vicksburg, but I would think it's relatively small downtown area would be an 8b. I remember in the past looking at the weather there, and NOAA used to use the airport between Vicksburg (which sits atop a bluff) and Tallulah, Louisiana (on lower, flat land...and I believe somewhat colder). So I suppose it's possible this may have biased Vicksburg down, but I never really did track it or  spend any time there, so can't speak to it directly.

And if you really want to get an earful, try asking some of the Tallahassee people on this forum how they feel about their entire city and surrounding rural area, which has a crazy assortment of microclimates, being painted with a broad "8b" brush by PRISM and the USDA...and also the western half and interior of peninsular Florida, where winter lows are surprisingly variable over short distances...in short, there are many, many shortcomings to using this map, and the best thing is for you to observe local weather stations on wunderground, and hopefully get a station of your own so you really know your situation.

And regardless of zones and microclimates, remember in the Deep South to subtract about 15-20 degrees from your zone when selecting large foundation trees, because every 20-50 years such temperatures are likely to occur, and I don't think anyone wants a monster tree to remove after a 1989-style freeze. In Natchez, even centuries-old live oaks there lost large limbs in the 4F low and lengthy ice-storm that Christmas. Many similar nightmares occurred throughout the south that year, including in Houston, Baton Rouge and New Orleans. 1835, 1899 and 1940 were rough analogs to that year, and there have been many others in between that were close.

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Michael Norell

Rancho Mirage, California | 33°44' N 116°25' W | 287 ft | z10a | avg Jan 43/70F | Jul 78/108F avg | Weather Station KCARANCH310

previously Big Pine Key, Florida | 24°40' N 81°21' W | 4.5 ft. | z12a | Calcareous substrate | avg annual min. approx 52F | avg Jan 65/75F | Jul 83/90 | extreme min approx 41F

previously Natchez, Mississippi | 31°33' N 91°24' W | 220 ft.| z9a | Downtown/river-adjacent | Loess substrate | avg annual min. 23F | Jan 43/61F | Jul 73/93F | extreme min 2.5F (1899); previously Los Angeles, California (multiple locations)

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The other above posters are probably correct.

However, I’ll also mention in some cases it could be as simple as them using bad data. USDA’s maps can be pretty flawed.

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I agree, no one should takes these maps as 100% accurate, its just a guideline.  You'll see people on here post about how they are only one street from a half zone warmer.  That's simply not the case.

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1 hour ago, mnorell said:

They are not "anti-microclimates." They are examples of the poor quality of these maps created at great cost and with much fanfare by the "PRISM" group in Oregon...but went across like a lead balloon to anyone who tracks weather/climate. It was announced during the many years of their development that these would take into account local variations with incredible detail, etc. and, sadly, that just isn't reflected in the maps. Even small urbanized areas can create a marked difference in microclimate. I used to live in Natchez, Mississippi, in the downtown grid just a few blocks from the bluff overlooking the Mississippi River. The downtown area, except for a couple of air-drained cold-spots (mostly creeks/gullies/"bayous"), is a zone 9a, while the surrounding countryside is mostly 8b or even colder (I had a Davis weather station as did/do several others there, and tracked the data for years). One of the problems is that NOAA often uses airports as defining weather stations for metro areas. The Natchez airport is located north of town on a grassy plain more inland from the river, and is markedly colder than the downtown area.

The maps also don't seem to take local geography and air-drainage into account. One example that I regularly experienced when driving back and forth from Baton Rouge to Natchez was the journey up and down the Homochitto Ridge, about 20 miles south of Natchez. On a cold, still, clear night, you could leave Woodville (a town to the south of the ridge) and, while driving up and over that ridge near the settlement called Doloroso, the car-thermometer would climb roughly 10 degrees; and back down as one traversed on down the other side into the Homochitto River basin. Yet this is not reflected on this map. I know there are many more examples of this (and of course this and any other warm slopes or frost-pocket/river-course low spots could have easily been modeled/generated with a desktop computer using USGS topo data).

Likewise, Baton Rouge, which is a fairly large, sprawling city nowadays, does have a warmer microclimate than the surrounding area. This is especially marked in the downtown/Government St. and Garden District areas. In the latter, there are large numbers of Live Oaks sheltering the streets and homes, adding several additional degrees to the Urban Heat Island. Also, many areas of Louisiana have large bodies of water, sometimes lakes, sometimes rivers, sometimes just boggy, swampy zones that aren't readily visible on maps. And it is in general a quite rural (or small town) area, and that makes it tricky to estimate just how the microclimates come and go. (There are some South Louisiana folks here on this forum who could elaborate on that, I'm sure.) And again, the Baton Rouge Airport is located north of town in a somewhat colder area (and temps there would usually track within a degree or two of the Natchez downtown grid, despite being 75 miles south of Natchez). So I would assume they relied on the airport readings to either define or bias the zone definition for the city of Baton Rouge.

I can't speak to the issue of Vicksburg, but I would think it's relatively small downtown area would be an 8b. I remember in the past looking at the weather there, and NOAA used to use the airport between Vicksburg (which sits atop a bluff) and Tallulah, Louisiana (on lower, flat land...and I believe somewhat colder). So I suppose it's possible this may have biased Vicksburg down, but I never really did track it or  spend any time there, so can't speak to it directly.

And if you really want to get an earful, try asking some of the Tallahassee people on this forum how they feel about their entire city and surrounding rural area, which has a crazy assortment of microclimates, being painted with a broad "8b" brush by PRISM and the USDA...and also the western half and interior of peninsular Florida, where winter lows are surprisingly variable over short distances...in short, there are many, many shortcomings to using this map, and the best thing is for you to observe local weather stations on wunderground, and hopefully get a station of your own so you really know your situation.

And regardless of zones and microclimates, remember in the Deep South to subtract about 15-20 degrees from your zone when selecting large foundation trees, because every 20-50 years such temperatures are likely to occur, and I don't think anyone wants a monster tree to remove after a 1989-style freeze. In Natchez, even centuries-old live oaks there lost large limbs in the 4F low and lengthy ice-storm that Christmas. Many similar nightmares occurred throughout the south that year, including in Houston, Baton Rouge and New Orleans. 1835, 1899 and 1940 were rough analogs to that year, and there have been many others in between that were close.

That was just what I needed, thanks for the in depth explanation. I figured that it had something to do with the creators of the map not getting correct data. It just didn't make any sense as to why those places would be colder.

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Do not trust Maps or the data. What grows…

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What you look for is what is looking

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  • 2 months later...
On 4/6/2023 at 12:23 PM, mnorell said:

They are not "anti-microclimates." They are examples of the poor quality of these maps created at great cost and with much fanfare by the "PRISM" group in Oregon...but went across like a lead balloon to anyone who tracks weather/climate. It was announced during the many years of their development that these would take into account local variations with incredible detail, etc. and, sadly, that just isn't reflected in the maps. Even small urbanized areas can create a marked difference in microclimate. I used to live in Natchez, Mississippi, in the downtown grid just a few blocks from the bluff overlooking the Mississippi River. The downtown area, except for a couple of air-drained cold-spots (mostly creeks/gullies/"bayous"), is a zone 9a, while the surrounding countryside is mostly 8b or even colder (I had a Davis weather station as did/do several others there, and tracked the data for years). One of the problems is that NOAA often uses airports as defining weather stations for metro areas. The Natchez airport is located north of town on a grassy plain more inland from the river, and is markedly colder than the downtown area.

The maps also don't seem to take local geography and air-drainage into account. One example that I regularly experienced when driving back and forth from Baton Rouge to Natchez was the journey up and down the Homochitto Ridge, about 20 miles south of Natchez. On a cold, still, clear night, you could leave Woodville (a town to the south of the ridge) and, while driving up and over that ridge near the settlement called Doloroso, the car-thermometer would climb roughly 10 degrees; and back down as one traversed on down the other side into the Homochitto River basin. Yet this is not reflected on this map. I know there are many more examples of this (and of course this and any other warm slopes or frost-pocket/river-course low spots could have easily been modeled/generated with a desktop computer using USGS topo data).

Likewise, Baton Rouge, which is a fairly large, sprawling city nowadays, does have a warmer microclimate than the surrounding area. This is especially marked in the downtown/Government St. and Garden District areas. In the latter, there are large numbers of Live Oaks sheltering the streets and homes, adding several additional degrees to the Urban Heat Island. Also, many areas of Louisiana have large bodies of water, sometimes lakes, sometimes rivers, sometimes just boggy, swampy zones that aren't readily visible on maps. And it is in general a quite rural (or small town) area, and that makes it tricky to estimate just how the microclimates come and go. (There are some South Louisiana folks here on this forum who could elaborate on that, I'm sure.) And again, the Baton Rouge Airport is located north of town in a somewhat colder area (and temps there would usually track within a degree or two of the Natchez downtown grid, despite being 75 miles south of Natchez). So I would assume they relied on the airport readings to either define or bias the zone definition for the city of Baton Rouge.

I can't speak to the issue of Vicksburg, but I would think it's relatively small downtown area would be an 8b. I remember in the past looking at the weather there, and NOAA used to use the airport between Vicksburg (which sits atop a bluff) and Tallulah, Louisiana (on lower, flat land...and I believe somewhat colder). So I suppose it's possible this may have biased Vicksburg down, but I never really did track it or  spend any time there, so can't speak to it directly.

And if you really want to get an earful, try asking some of the Tallahassee people on this forum how they feel about their entire city and surrounding rural area, which has a crazy assortment of microclimates, being painted with a broad "8b" brush by PRISM and the USDA...and also the western half and interior of peninsular Florida, where winter lows are surprisingly variable over short distances...in short, there are many, many shortcomings to using this map, and the best thing is for you to observe local weather stations on wunderground, and hopefully get a station of your own so you really know your situation.

And regardless of zones and microclimates, remember in the Deep South to subtract about 15-20 degrees from your zone when selecting large foundation trees, because every 20-50 years such temperatures are likely to occur, and I don't think anyone wants a monster tree to remove after a 1989-style freeze. In Natchez, even centuries-old live oaks there lost large limbs in the 4F low and lengthy ice-storm that Christmas. Many similar nightmares occurred throughout the south that year, including in Houston, Baton Rouge and New Orleans. 1835, 1899 and 1940 were rough analogs to that year, and there have been many others in between that were close.

BINGO!!!!😀😄

This is one of the big problems I have with airport stations, outside the local microclimates and assumed to be representative of it all. I've always suspected the USDA zone map was off too after they had some 8a in Florida but this proves they got messy.
I too like to go to the wunderground stations over the airports to monitor the Southeast US, glad to see I'm not alone in doing that.😎

Just stumbled across this thread and I'd like to say it's very related to the thread I just made about Southeast US airports often being cold spots. Aside from all the above good reasons listed here, Southeast US airports are deforested for both the airport and the weather station and this makes the airport readings artificially cold in any airport where this happened because heat-trapping trees are a natural part of climate, but without them low temperatures get massively and disproportionately colder (and the sandy soil most US airports have doesn't exactly help the matter either).
Here is the thread, if you haven't seen it you will probably find it a good read given your knowledge here.😉
https://www.palmtalk.org/forum/topic/79904-why-southeast-us-airports-are-often-cold-spots/

I wish laypeople would stop taking this old USDA zone map as gospel in general, even if they don't know about the microclimates and artificially cold airports it's very obvious it's outdated because it's 1976-2005 and we're in 1991-2020 (with 2001-2030 coming up slowly but surely). I've had to deal with a ton of people on City-Data weather who think so and it's gotten quite annoying at this point, so glad to see Palmtalk sees the big problems.😆

 

Edited by Can't think of username
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2 hours ago, Can't think of username said:

BINGO!!!!😀😄

This is one of the big problems I have with airport stations, outside the local microclimates and assumed to be representative of it all. I've always suspected the USDA zone map was off too after they had some 8a in Florida but this proves they got messy.
I too like to go to the wunderground stations over the airports to monitor the Southeast US, glad to see I'm not alone in doing that.😎

Just stumbled across this thread and I'd like to say it's very related to the thread I just made about Southeast US airports often being cold spots. Aside from all the above good reasons listed here, Southeast US airports are deforested for both the airport and the weather station and this makes the airport readings artificially cold in any airport where this happened because heat-trapping trees are a natural part of climate, but without them low temperatures get massively and disproportionately colder (and the sandy soil most US airports have doesn't exactly help the matter either).
Here is the thread, if you haven't seen it you will probably find it a good read given your knowledge here.😉
https://www.palmtalk.org/forum/topic/79904-why-southeast-us-airports-are-often-cold-spots/

I wish laypeople would stop taking this old USDA zone map as gospel in general, even if they don't know about the microclimates and artificially cold airports it's very obvious it's outdated because it's 1976-2005 and we're in 1991-2020 (with 2001-2030 coming up slowly but surely). I've had to deal with a ton of people on City-Data weather who think so and it's gotten quite annoying at this point, so glad to see Palmtalk sees the big problems.😆

 

Wunderground is great for that. We have the exact same issue here in the UK with the official weather stations all in parks and airports recording lower temperatures than the city itself. The long term data here also isn't representative of the temperatures we see nowdays, our summers are significantly warmer than they used to be on average and it looks like the trend is towards even warmer summers in the future. There are also plenty of people here in the UK that will argue against the proof and stick to their inaccurate hardiness zone maps, but if they are right then why are king palms and kentias able to grow unprotected! Some hardiness maps for example show the city of London as a zone 9a, despite the fact the weather stations there average as a zone 10a. There are howea forsteriana's, swiss cheese plants, ensete maurelii's, bougainvilleas and Norfolk Island pines ect that survive even the coldest winters there with no damage, sure seems like zone 9a🤣.  It's nice to see that other people are aware of this issue.

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1 hour ago, Foxpalms said:

Wunderground is great for that. We have the exact same issue here in the UK with the official weather stations all in parks and airports recording lower temperatures than the city itself. The long term data here also isn't representative of the temperatures we see nowdays, our summers are significantly warmer than they used to be on average and it looks like the trend is towards even warmer summers in the future. There are also plenty of people here in the UK that will argue against the proof and stick to their inaccurate hardiness zone maps, but if they are right then why are king palms and kentias able to grow unprotected! Some hardiness maps for example show the city of London as a zone 9a, despite the fact the weather stations there average as a zone 10a. There are howea forsteriana's, swiss cheese plants, ensete maurelii's, bougainvilleas and Norfolk Island pines ect that survive even the coldest winters there with no damage, sure seems like zone 9a🤣.  It's nice to see that other people are aware of this issue.

I am not all that familiar with the climate of anywhere in England nor am I as familiar with those plants as you (still learning), but London's hardiness zone, plants, stations, and maps have all been brought up a ton of times on City-Data - with exactly what you are talking about, way too many people are insisting despite what the London natives on that site are telling them on 9a or even 8b. Believe it or not the discussion on there has - multiple times - even gotten bad enough to accuse the London natives of intentionally trying to make their climate warmer than it is, as if Wunderground stations and plants do that.🤣

Another problem in these kinds of discussions that I have run into is the automatic assumption that airport to airport is apples to apples because it is airport to airport.....yeah no. I don't know if anywhere in England has more urban airport weather stations but if it does you may have or may eventually run into this problem.
The most jarring example that comes to mind is the following: https://www.city-data.com/forum/weather/3366619-what-like-experience-4-distinct-seasons-20.html#post65093495

No reasonable argument can be made that the Boston airport (the warmest place in the entire metro, right downtown and on the water) is apples to apples with the Tallahassee airport that not only has been found to be artificially very cold by the results of 3 studies, but is so much so that it has cold anomaly-season low temperatures 0.5C colder than Columbus Georgia airport 2 degrees further north (which for reference would also of course be artificially cold due to forest clearing, even if not as much so).  And yet apparently their both being airports suddenly would make all of that irrelevant - as well as the Wunderground stations apparently causing more problems than they solve when the TALLAHASSEE WEATHER BRANCH LITERALLY USES THEM.🙄

Have you ever ran into that problem? I would say it's just as bad as the blind faith in these USDA zone maps - the best judge of apples to apples is how representative of the city the station is, and whether that representation or lack thereof is artificial (from either heat island or cooling deforestation) or natural. Whether the station is an airport or not is irrelevant to whether it is apples to apples with another equally representative station.
I guess this is one of the better sites to discuss this. So glad to see that on here, the actual climates are given their due.

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1 hour ago, Can't think of username said:

I am not all that familiar with the climate of anywhere in England nor am I as familiar with those plants as you (still learning), but London's hardiness zone, plants, stations, and maps have all been brought up a ton of times on City-Data - with exactly what you are talking about, way too many people are insisting despite what the London natives on that site are telling them on 9a or even 8b. Believe it or not the discussion on there has - multiple times - even gotten bad enough to accuse the London natives of intentionally trying to make their climate warmer than it is, as if Wunderground stations and plants do that.🤣

Another problem in these kinds of discussions that I have run into is the automatic assumption that airport to airport is apples to apples because it is airport to airport.....yeah no. I don't know if anywhere in England has more urban airport weather stations but if it does you may have or may eventually run into this problem.
The most jarring example that comes to mind is the following: https://www.city-data.com/forum/weather/3366619-what-like-experience-4-distinct-seasons-20.html#post65093495

No reasonable argument can be made that the Boston airport (the warmest place in the entire metro, right downtown and on the water) is apples to apples with the Tallahassee airport that not only has been found to be artificially very cold by the results of 3 studies, but is so much so that it has cold anomaly-season low temperatures 0.5C colder than Columbus Georgia airport 2 degrees further north (which for reference would also of course be artificially cold due to forest clearing, even if not as much so).  And yet apparently their both being airports suddenly would make all of that irrelevant - as well as the Wunderground stations apparently causing more problems than they solve when the TALLAHASSEE WEATHER BRANCH LITERALLY USES THEM.🙄

Have you ever ran into that problem? I would say it's just as bad as the blind faith in these USDA zone maps - the best judge of apples to apples is how representative of the city the station is, and whether that representation or lack thereof is artificial (from either heat island or cooling deforestation) or natural. Whether the station is an airport or not is irrelevant to whether it is apples to apples with another equally representative station.
I guess this is one of the better sites to discuss this. So glad to see that on here, the actual climates are given their due.

The situation in the UK, in regards to people's imaginations running wild has gotten even more stupid in recent years. Pretty much every time Heathrow records temperatures over 80f, hundreds of people seems to be convinced that only happens because of the tarmac on the runway, despite the fact the weather station is situated north of there on a patch of grass.  Yesterday there were plenty of those comments though they looked a bit silly when later on another weather station a couple miles away with no airport recorded a higher temperature on a field! A lot of people also seem to be under the impression the planes are making the temperature readings at Heathrow much higher, despite the fact airliner planes don't create much heat just a lot of wind. They not are fighter jets with afterburners. The only real argument that can be made is wunderground stations might not be accurate, however if it's a Davis weather station then in my opinion the temperature readings are likely accurate. Especially when nearby stations are showing the same, or similar temperature readings. Some people are even trying to accuse the Metoffice of releasing chemicals into the sky to try and trap the heat in to get higher temperature readings, despite the fact that would reduce the temperature and the winds would just blow the chemicals away 😂. Their evidence for this are contrails from planes! A lot of people here also don't seem to understand the city itself gets warmer than fields and airports due to us having a massive urban heat island effect. The buildings in London are also extremely dense, especially in central London.  The hardiness zones here are 9a, 9b and 10a. The only airport that has the urban heat island effect is London city airport, but it's still not as strong as the urban heat island is in central London. 

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On 6/11/2023 at 2:16 PM, Foxpalms said:

The situation in the UK, in regards to people's imaginations running wild has gotten even more stupid in recent years. Pretty much every time Heathrow records temperatures over 80f, hundreds of people seems to be convinced that only happens because of the tarmac on the runway, despite the fact the weather station is situated north of there on a patch of grass.  Yesterday there were plenty of those comments though they looked a bit silly when later on another weather station a couple miles away with no airport recorded a higher temperature on a field! A lot of people also seem to be under the impression the planes are making the temperature readings at Heathrow much higher, despite the fact airliner planes don't create much heat just a lot of wind. They not are fighter jets with afterburners. The only real argument that can be made is wunderground stations might not be accurate, however if it's a Davis weather station then in my opinion the temperature readings are likely accurate. Especially when nearby stations are showing the same, or similar temperature readings. Some people are even trying to accuse the Metoffice of releasing chemicals into the sky to try and trap the heat in to get higher temperature readings, despite the fact that would reduce the temperature and the winds would just blow the chemicals away 😂. Their evidence for this are contrails from planes! A lot of people here also don't seem to understand the city itself gets warmer than fields and airports due to us having a massive urban heat island effect. The buildings in London are also extremely dense, especially in central London.  The hardiness zones here are 9a, 9b and 10a. The only airport that has the urban heat island effect is London city airport, but it's still not as strong as the urban heat island is in central London. 

I needed a laugh today, thanks!🤣😄That beats what City-Data says, London heat is accused for exaggeration there but this is right up next level for that.

If this starts back up on there I just might link this.

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  • 2 months later...
On 6/11/2023 at 5:59 AM, Can't think of username said:

BINGO!!!!😀😄

This is one of the big problems I have with airport stations, outside the local microclimates and assumed to be representative of it all. I've always suspected the USDA zone map was off too after they had some 8a in Florida but this proves they got messy.
I too like to go to the wunderground stations over the airports to monitor the Southeast US, glad to see I'm not alone in doing that.😎

Just stumbled across this thread and I'd like to say it's very related to the thread I just made about Southeast US airports often being cold spots. Aside from all the above good reasons listed here, Southeast US airports are deforested for both the airport and the weather station and this makes the airport readings artificially cold in any airport where this happened because heat-trapping trees are a natural part of climate, but without them low temperatures get massively and disproportionately colder (and the sandy soil most US airports have doesn't exactly help the matter either).
Here is the thread, if you haven't seen it you will probably find it a good read given your knowledge here.😉
https://www.palmtalk.org/forum/topic/79904-why-southeast-us-airports-are-often-cold-spots/

I wish laypeople would stop taking this old USDA zone map as gospel in general, even if they don't know about the microclimates and artificially cold airports it's very obvious it's outdated because it's 1976-2005 and we're in 1991-2020 (with 2001-2030 coming up slowly but surely). I've had to deal with a ton of people on City-Data weather who think so and it's gotten quite annoying at this point, so glad to see Palmtalk sees the big problems.😆

 

I've mentioned in another thread awhile back that people in my area think the winters are colder than they actually are. I think the original USDA hardiness zone map from like 1960 or so is one of the reasons why. It seems there wasn't enough data to properly map the western US at the time, and so that map paints with a very broad brush. Putting huge swaths of high desert in either zone 4 or 5, can't remember which one. The most recent map is much better, but even then it's data from 1975 to 2005, meaning the most recent data is almost 20 years old. Even barring the old data, there are still small areas that seem to be wrong on the map. It's super difficult to map out every little canyon and valley in the west.

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16 minutes ago, Southwesternsol said:

I've mentioned in another thread awhile back that people in my area think the winters are colder than they actually are. I think the original USDA hardiness zone map from like 1960 or so is one of the reasons why. It seems there wasn't enough data to properly map the western US at the time, and so that map paints with a very broad brush. Putting huge swaths of high desert in either zone 4 or 5, can't remember which one. The most recent map is much better, but even then it's data from 1975 to 2005, meaning the most recent data is almost 20 years old. Even barring the old data, there are still small areas that seem to be wrong on the map. It's super difficult to map out every little canyon and valley in the west.

Not sure if this helps you out or not but here's the " 2012 " update of the map for the 4 - corners region..  Still not perfect ( ...and likely outdated now..  A new one is needed, asap. ) but i myself like the info provided by the maps off this site vs the more " general " maps which, as you mention, don't really capture all the " detailed "  details when it comes to how topography effects everything here. 

Hopefully when a new one is put together, it is even more detailed.

AZ

Screenshot2023-08-24at18-04-23ArizonaInteractive2012USDAPlantHardinessZoneMap.png.b3708999dcf584a7d547a00d6b309472.png

UT
Screenshot2023-08-24at17-53-42UtahInteractive2012USDAPlantHardinessZoneMap.png.aca6551894c070bbc10200f4a7225ca9.png

CO

Screenshot2023-08-24at17-52-10ColoradoInteractive2012USDAPlantHardinessZoneMap.png.6cf7fd96f995a9403b00276d4a06f3f3.png

N.M.

Screenshot2023-08-24at17-51-27NewMexicoInteractive2012USDAPlantHardinessZoneMap.png.ef72237e46c4120916dd834105941480.png

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2 hours ago, Silas_Sancona said:

Not sure if this helps you out or not but here's the " 2012 " update of the map for the 4 - corners region..  Still not perfect ( ...and likely outdated now..  A new one is needed, asap. ) but i myself like the info provided by the maps off this site vs the more " general " maps which, as you mention, don't really capture all the " detailed "  details when it comes to how topography effects everything here. 

Hopefully when a new one is put together, it is even more detailed.

AZ

Screenshot2023-08-24at18-04-23ArizonaInteractive2012USDAPlantHardinessZoneMap.png.b3708999dcf584a7d547a00d6b309472.png

UT
Screenshot2023-08-24at17-53-42UtahInteractive2012USDAPlantHardinessZoneMap.png.aca6551894c070bbc10200f4a7225ca9.png

CO

Screenshot2023-08-24at17-52-10ColoradoInteractive2012USDAPlantHardinessZoneMap.png.6cf7fd96f995a9403b00276d4a06f3f3.png

N.M.

Screenshot2023-08-24at17-51-27NewMexicoInteractive2012USDAPlantHardinessZoneMap.png.ef72237e46c4120916dd834105941480.png

I'm not saying the map is bad, I'm just agreeing with Can't think of a username's point that people shouldn't treat it as gospel. There's some nuances you've got to keep in mind

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10 minutes ago, Southwesternsol said:

I'm not saying the map is bad, I'm just agreeing with Can't think of a username's point that people shouldn't treat it as gospel. There's some nuances you've got to keep in mind

Yep,  That's one reason i stopped using it..  As " decent as the Plant Maps version is, it still doesn't capture things correctly.. I shouldn't have a slim, but healthy 15+yr old Tamarind, large Royal Poinciana, and 10ft tall Papaya ( neighbors ) in my ..supposedly.. zone 9 neighborhood.


Have a Bursera sp. from coastal S.W. Mexico ( zone 13 ) that should have cringed it's winter outside here.. Headed toward winter #7 content as can be ( Though i'm sure it would be even happier in the ground,  rather than a large pot, lol )

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