USDA Cold Hardiness off by a zone?

[Dimovi]

My understanding is that USDA calculates cold hardiness by taking the lowest temperature each year over 30 years and averaging them, but when I made a spreadsheet for Austin, TX (middle of 8b) my calculations for 2012 put us in the middle of 9a, and in 2020 we are at 23.7F

Is that not the case?

I still find the system a bit odd as plants don't care about averages and mostly care about extreme lows, so I did also calculate the minimum for last 30 years.

Here is the spreadsheet if anyone cares to try with your weather data.

https://drive.google.com/file/d/1riGDrUzzmqQONdHkVbbyIfNi65unMh4T/view?usp=sharing

 

 

 

[kinzyjr]

@Dimovi

Interesting stats.  A bunch of us Floridians were working on something similar for our respective areas: https://www.palmtalk.org/forum/index.php?/topic/6179-make-your-own-zone-map/

[Austinpalm]

1 hour ago, Dimovi said:

My understanding is that USDA calculates cold hardiness by taking the lowest temperature each year over 30 years and averaging them, but when I made a spreadsheet for Austin, TX (middle of 8b) my calculations for 2012 put us in the middle of 9a, and in 2020 we are at 23.7F

Is that not the case?

I still find the system a bit odd as plants don't care about averages and mostly care about extreme lows, so I did also calculate the minimum for last 30 years.

Here is the spreadsheet if anyone cares to try with your weather data.

https://drive.google.com/file/d/1riGDrUzzmqQONdHkVbbyIfNi65unMh4T/view?usp=sharing

 

 

 

Am curious which weather station/location are being used for this data? Camp Mabry is in west central Austin and is usually a bit warmer than other sites, but ABIA and the old Austin Mueller airport are usually a little colder than what I see here in south Austin.  I have believed for some time now that the Austin metro is zone 9a on average, due to the heat island effect.  Outside of town to the north and west is still 8b. South and east are not quite as cool as the areas north and west of town. 

I have a friend downtown, near the Colorado River and it appears to me that they have recently been having 9b or 10a winters.  There is actually an epiphyllum oxypetalum growing on a Sabal in that area.  Not sure how long it have been there, but by the size, looked to have survived for a few years.

Just my 2 cents.

[necturus]

The last USDA zone update incorporated the 1980s. That was a cold decade and brings down the average annual lows significantly. If you look at the zone maps over time, you see that the original ones from the 60s are similar to the ones we have now, but the maps in the 80s dropped the zones across the board such that much of Houston was zone 8.  The last few decades have been very mild, so we're running warmer than any previous USDA zone map.

So yes, the next update will bump up most zones by a half zone. Most of Houston will be zone 9B, and the immediate coast and Galveston will be zone 10A.

[Allen]

For palms your absolute lows and duration of cold are the main issue ultimately anyway.  

[ColdBonsai]

Very interesting. I wasn't sure how many years of data the USDA used to calculate a zone.  Looks like I could qualify for zone 7b! Which would explain the rare, but large, windmill palm specimens that a few people have had over the years.

Edited June 22, 2020 by ColdBonsai

[Dimovi]

4 hours ago, Austinpalm said:

Am curious which weather station/location are being used for this data? Camp Mabry is in west central Austin and is usually a bit warmer than other sites, but ABIA and the old Austin Mueller airport are usually a little colder than what I see here in south Austin.  I have believed for some time now that the Austin metro is zone 9a on average, due to the heat island effect.  Outside of town to the north and west is still 8b. South and east are not quite as cool as the areas north and west of town. 

I have a friend downtown, near the Colorado River and it appears to me that they have recently been having 9b or 10a winters.  There is actually an epiphyllum oxypetalum growing on a Sabal in that area.  Not sure how long it have been there, but by the size, looked to have survived for a few years.

Just my 2 cents.

The data since 1939 is from Camp Mabry, before that was from UT.
I compared the last 4 years between Camp Mabry and Burgstrom Airport, two years were the same and two years Bergstrom was a degree warmer. I didn't bother getting all 30 years, but it seems unlikely it would affect the averages by one zone.

[Dimovi]

4 hours ago, necturus said:

The last USDA zone update incorporated the 1980s. That was a cold decade and brings down the average annual lows significantly. If you look at the zone maps over time, you see that the original ones from the 60s are similar to the ones we have now, but the maps in the 80s dropped the zones across the board such that much of Houston was zone 8.  The last few decades have been very mild, so we're running warmer than any previous USDA zone map.

So yes, the next update will bump up most zones by a half zone. Most of Houston will be zone 9B, and the immediate coast and Galveston will be zone 10A.

The last USDA zone update was in 2012 and for that year (averaging 30 years back) I got 22.6F
If fact Austin should have been in 9a at 20.2F since 2000 (averaging lows from 1971 to 2000).
I understand USDA does not update the map every year, but this is well before 2012.
And it has been mostly going up since 2000.

[TexasColdHardyPalms]

Nvm. I see it now

[Dimovi]

3 hours ago, Allen said:

For palms your absolute lows and duration of cold are the main issue ultimately anyway.  

Yes, that is why I made some tabs with absolute low in last 30, 20 and 10 years.

I have no easy way to account for duration, but I did use the minimum of the lows within a period to create my own hardiness zone

[Dimovi]

1 minute ago, TexasColdHardyPalms said:

I must be looking at the wrong file or something but 2017 and 2011 low temps were way lower than the 22f posted in that chart. 

The chart shows the average of all lows over 30 year period.

So, for 2017 the value was obtained by averaging all lows from 1986 to 2017 and the value for 2011 was obtained by averaging the lows from 1980 to 2011.

The temperatures for 2017 and 2011 affected the averages by pulling them down a bit.

[JLM]

I am slowly filling in data from my local weather station. Im using wunderground, thats all i can find that goes back really far. Although, the data for this station doesnt start until February 1945

[JLM]

@Dimovi What did you use to get all the data? Too many data holes on wunderground especially in the 70s

[kinzyjr]

@JLM

Wunderground seems to have introduced quite a few holes, at least for KLAL (Lakeland Linder International). 

I did a Wunderground data dump back in 2018, and then another one just recently to catch everything up to current date.  There were holes and amended numbers in a lot of the monthly records, so I ended up having to re-dump the currently available years and fill in the holes using data from the old dump, NOAA, AccuWeather, and some data I had stashed away from Weather.com. 

I managed to get a pretty solid table of data to use for that Make Your Own Zone Map thread.  There was a fairly wide range of numbers given for supposedly the same airport location for several important freeze dates (2008/2010/2018) by the above sources.

If you want a link that is very helpful with averages/lows/etc., @JJPalmer shared a link on the Make Your Own Zone Map thread that can be modified to get weather in other geographical areas.  Here's a link that will help you in your area: https://w2.weather.gov/climate/index.php?wfo=tae

[JLM]

@kinzyjr

It will only let me go back 1 year for my area (Mobile). Is there a way to go back further?

[Xenon]

16 minutes ago, JLM said:

@kinzyjr

It will only let me go back 1 year for my area (Mobile). Is there a way to go back further?

https://w2.weather.gov/climate/xmacis.php?wfo=mob

You can also access and order (for free) even more data directly from the NCDC 

[Dimovi]

@JLM for this analysis I used https://www.currentresults.com/Yearly-Weather/USA/extreme-annual-usa-index-low-temperature.php

In the past I have also gotten the raw weather data from NOAA described here https://www.climate.gov/maps-data/dataset/past-weather-zip-code-data-table
I had to write some python scripts to crunch the data from NOAA as it has too much information with data for every day.

[Xenon]

16 minutes ago, Dimovi said:

@JLM for this analysis I used https://www.currentresults.com/Yearly-Weather/USA/extreme-annual-usa-index-low-temperature.php

In the past I have also gotten the raw weather data from NOAA described here https://www.climate.gov/maps-data/dataset/past-weather-zip-code-data-table
I had to write some python scripts to crunch the data from NOAA as it has too much information with data for every day.

much easier to visit the local NWS portal (i.e NWS Austin/San Antonio) -> select "Climate and Past Weather" -> Local Data -> NOWData

[Dimovi]

@Xenon I can't find it. Can you share a link?

[kinzyjr]

7 hours ago, JLM said:

@kinzyjr

It will only let me go back 1 year for my area (Mobile). Is there a way to go back further?

I was able to access more than one year. 

1. Make sure you are on the NOWData tab
2. Select the weather station of your choosing
3. Select Monthly summarized data for your Product
4. Enter a date range.  If you want all of the history, it may take some experimenting.  Select for Min Temp and Daily Minimum in the Variable and Summary dropdowns.
5. Click Go.

You can see some of the years I selected for Mobile are before there were records, but in March 1872 the records start.

[Xenon]

7 hours ago, Dimovi said:

@Xenon I can't find it. Can you share a link?

https://w2.weather.gov/climate/xmacis.php?wfo=ewx

[Dimovi]

1 hour ago, Xenon said:

https://w2.weather.gov/climate/xmacis.php?wfo=ewx

Thanks! This is useful

[JLM]

Thanks @kinzyjr!!

I decided to start over with a new sheet with new data. One section will be from 1989-2019 (30 years), then the 30 years before 1989 in another section. 

[JLM]

With all the data put together and averaged over a 30 year period, this is what i found for these locations.

I chose the Pensacola Regional Airport and Robertsdale, AL. For Pensacola, it has gone from a warm 8b during the 1959-1988 period to a warm 9a in the 1989-2019 period.

Robertsdale has gone from a warm 8b in the 1959-1988 period to a cold 9a in the 1989-2019 period. The current map is correct in terms of the 1976-2005 data. But my area is 9a since 1989. 

I dont see why Pensacola doesnt have queens all over the downtown area, and the beach. There are 2 queens at Hemingway's Island Grill which have been there for a decent amount of time. They are not being taken care of though. I also saw a bismarck at a home in Pensacola Beach but i cant find it on street view.  This bismarck has a clear 10 feet of trunk from what i could see. I will keep looking!

Here are the queens: https://www.google.com/maps/@30.3353891,-87.1430515,3a,46.2y,13.06h,101.56t/data=!3m6!1e1!3m4!1skZrbGp5IFBa61cI1qoSabQ!2e0!7i16384!8i8192