Where Do You Measure Your Temperature?

[Kathryn]

Everyone is posting about the low temperatures in their yard versus local weather stations. Where in your yard to you measure your temperatures? How many thermometers do you have? What were your various reading?

I have one min/max thermometer just outside my bedroom about 1 foot from my house and 1 foot from the ground. This one had a low of 34ºF Thursday morning. I have many smaller palms in this location - including a potted Chamaedorea oblongata that did just fine.

I have another min/max thermometer in the same area, but it is 6 feet from my house and six feet from the ground. This one had a low of 27ºF Thursday morning. I’m not sure how cold the rest of my yard may have been. I guess I might get a couple more thermometers for the next cold snap.

I live in Destrehan and various sources list the low anywhere from 23 to 28ºF, but I don’t know where these measurements were actually recorded. The New Orleans International Airport is 10 miles east of my house and had an official low of 28ºF with the temperature at or below freezing for about 6 hours.

The only plants showing damage so far are a few spiral gingers that did not have overhead protection.

[spockvr6]

Kathryn-

This is a good topic as how one measures the temperature makes  ahuge difference in the reported results.

In my opinion, the most accurate and trustworthy readings will come from an accurate sensor placed into a fan ventilated enclosure placed at 5-6 ft above grade.

Measurements taken in this manner will be on par with those from "official" stations and not subjected to false readings.

[sonoranfans]

(Kathryn @ Jan. 04 2008,11:35)

QUOTE

Everyone is posting about the low temperatures in their yard versus local weather stations. Where in your yard to you measure your temperatures? How many thermometers do you have? What were your various reading?

I have one min/max thermometer just outside my bedroom about 1 foot from my house and 1 foot from the ground. This one had a low of 34ºF Thursday morning. I have many smaller palms in this location - including a potted Chamaedorea oblongata that did just fine.

I have another min/max thermometer in the same area, but it is 6 feet from my house and six feet from the ground. This one had a low of 27ºF Thursday morning. I’m not sure how cold the rest of my yard may have been. I guess I might get a couple more thermometers for the next cold snap.

I live in Destrehan and various sources list the low anywhere from 23 to 28ºF, but I don’t know where these measurements were actually recorded. The New Orleans International Airport is 10 miles east of my house and had an official low of 28ºF with the temperature at or below freezing for about 6 hours.

The only plants showing damage so far are a few spiral gingers that did not have overhead protection.

I have two shielded(from rain) wireless remote sensors(temp+humidity) that send signals to my two weather stations.  The remote sensors are the size of my fist and clip onto a mount.  Typically, I measure at about 5' above ground, and I can move the sensor around the yard as it is mounted to a (camera)tripod.  In AZ the difference in winter lows between under the canopy overnight and out in the open(w/ no wind at all) is about 4-5 F.  Overhead canopy is much more important to the temp reading than the proximity of the house as heat rises.  Within 6' of the house may be 1F or so compared to 25 feet away, except in the case where the thermosat is between 2 houses(warmer).  Wind block is also important as the ground heats the air and it(warm air) may blow away, to be replaced by cold air.  This is why I have decided to plant fast growing overhead canopy and more windblock near my Bizzies, an area that I have identified as a relative cold spot in my yard.

Overhead canopy traps heat that rises from the earth after sundown, as the earth cools well after the air when the sun goes down.  The sun heats the earth and the earth is a black body radiator that then, in turn, heats air close to the ground first.  You want to trap that heated aoir as much as possible with canopy and windblock.  I think the effect is greater here in AZ, as we have big differences between daytime and night time temps due to the low humidity, and more solar heating of the ground due to the lack of clouds and moisture in the air.  I think in La, you would need to move the sensors around your yard, under canopy and out in the open to see how your microclimates differ.

[Steve]

The sensor to my weather station is 10-15 ft from my house, and approx 6 feet off the ground.  I have found it to be very consistent with other weather stations in my area and with reports from the closest airport and other nearby cities.  It has a dome similar to the one Larry pictured to protect from false readings due to sunshine and rain.

I have the weather station positioned diagonally from the corner of my house.  I think being 10-15 feet from the house gives some false readings on wind speed sometimes because of currents created by the house.  My wife is not crazy about a metal pole with weather equipment sitting in the middle of the yard, so I can deal with a little trouble with the wind speed accuracy.  Other than that I love my weather station.

[mnorell]

The cheap digital sensors sold widely at Wal-Mart and Big Box stores have dubious accuracy and must be placed somewhere that receives no direct sunshine, so they are only really usable to measure temp under canopy (and are relatively useful for that purpose if you forgive the inaccuracy). I use a Davis Vantage Pro2 wireless unit, with proper shielding, rainmeter, windmeter, etc. This is mounted atop a fence a short distance from the house, under open sky for accuracy in measuring true air temp for unprotected plants, however a large cherry-laurel hedge to the north screws up the wind measurement. But for temperature these units are remarkably accurate and if you look at the Google map feature on wunderground you will see how closely in agreement these units are across a region or in close proximity (taking into account microclimates such as urban heat-island, topography, etc.). These units are about $500 if you look around for the best price for a wireless model, and they transmit to a nice backlit console that hooks into your computer, and there is great software available out there for measuring and storing this info. If you're into measuring your climate and the weather, these are worth every penny!!

[spockvr6]

(mnorell @ Jan. 04 2008,18:51)

QUOTE

If you're into measuring your climate and the weather, these are worth every penny!!

Agreed Michael....the Davis units seem to be tops for the residential type models.

I was too cheap, so I ended with an Orengon Scientific.  But, some corrleation work with some calibrated meters from work and my homemade fan ventilated enclosure have made a system that I know is accurate.

[glbower]

Michael -- I have been trying to decide between the Davis Pro2 and a cheaper Oregon Scientific model. What does the Davis have going for it that makes it worth the extra bucks? Anyone else using the Davis?

[freakypalmguy]

The Davis units have the highest level of accuracy. For example temperature is +/- 1F whereas the Oregon Scientific unit is +/- 2 to 6F.

I just bought a Honeywell TE 923W weather station and it is rated at +/- 2F for 200$ from Ambient Weather.com.

So far I am impressed with the unit, it was easy to set up and the components seem well built.

Here is a link to A Comparison of Home Weather Stations

Matt

[freakypalmguy]

Placement of a thermometer is very important. Too low and you can pick up radiant heat/cold from lawns, concrete, asphalt, etc. Direct sunlight = false readings.

A thermometer should be placed in the shade facing north on a building or fence so it does not ever get direct sunlight. It should be in an area of free air circulation. The international standard for valid air temerature measurement is 4feet above the ground.

Ideally it should be place in a Stevenson Screen (white slatted box) or like Larry's above. El Hoagie built his own also, here's a pic from another thread. He also posted a link to a site explaining how to make one, I just can't find it yet. Hoagie, ya out there?

[freakypalmguy]

Here it is,  How to Make a Stevenson Screen .

I think Matty made one too.

Matt

[freakypalmguy]

And here is a DIY of the Box Type Stevenson Screen

Matt

[_Keith]

I may be a bit different, but since I am only interested in measuring temps as they impact my plants, wouldn't I want a sensor that "would" be affected by radiant cold?  Here, it has far more effect on my plants in a normal winter, than advective cold.

keith

[freakypalmguy]

Hi Keith,

Absolutely, if you want to find the microclimates around your yard you can place them anywhere. I have a few spread out as well for that reason.

Matt

[Palmy]

I have 4 stations scattered throughout the yard.

1- 1 foot from house south facing wall.

2-  about 20 feet from my house and about 10 feet from the pool about 4 feet high on a tree.

3- On down the hill about 200 feet from my house

4- one in my garden about 4 feet high on a fence.

Perhaps I should put one higher up.

[ariscott]

(glbower @ Jan. 05 2008,22:56)

QUOTE

Michael -- I have been trying to decide between the Davis Pro2 and a cheaper Oregon Scientific model. What does the Davis have going for it that makes it worth the extra bucks? Anyone else using the Davis?

We are using LaCrosse WS3600 and it is not very accurate, IMO. We had manual rain gauge on a pole in the middle of the my cleared property (so very little error) and it was always 10% less on the weather station. Also, I have to reset it all the time... Temperature reading is not bad though.

3 of weather freaks that I know use Davis Pro2 and theirs are more reliable and pretty accurate (they compared it to the BOM about 2km away). If you can afford it, definitely get Davis Pro2. That is what we are getting next time...

Regards, Ari

[Big Tex]

I have a thermometer and weather sensor located about 20 yards from my house and about 1 foot off the ground.

[sonoranfans]

(keiththibodeaux @ Jan. 06 2008,11:43)

QUOTE

I may be a bit different, but since I am only interested in measuring temps as they impact my plants, wouldn't I want a sensor that "would" be affected by radiant cold?  Here, it has far more effect on my plants in a normal winter, than advective cold.

keith

Very true, its the temps that impact the plant.  For many palms, thats the bud height temps where they are planted.  When the sun is up, I dont really care about the temps, the overnight lows are most important.  In places like the desert where temps change rapidly in both directions a sensor housing with a large thermal mass will miss the low temp, as will any sensor near much concrete.  If the palm is planted there, thats where the snesor should be.  I generally keep the sensor out of the way of the early morning sun, though.  Being able to move the sensor around is also important if there are variations in the ambient temps as are typical in drier climates.  I have tested my sensor versus a labratory thermometer to within about 0.3 degrees near freezing, dont think its all that high tech to provide good sensors for a $69 weather station.  If they are off 1-1.5 degrees at 100F I dont care about that.

In wet climates, the temperatures will be more uniform around the yard as moisture damps temperature changes, so a fixed weather station isnt as much of a risk.  Last winter I had two plant species all around my yard, some were defolliated, some were not.  That was my first clue that temps around the yard were not uniform here in AZ.  This year, the orange esperanza under canopy did not burn at all, but in the open there was plenty of leaf burn.