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> thermometer placement/building radiation
kpk33x
post May 31 2013, 12:29 PM
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Joined: 18-July 05
From: Mahomet, IL
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I bought a new weatherstation (La Crosse Technology WS-2812U-IT) and had not taken the old thermometer down. The new sensor is attached to a fencepost 6' high in the back of my yard just under the first branches of a bank of pine trees. Its the only place that never gets sun. The old one was attached to the fencepost next to my house also 6' up near no vents or windows and got sun between late morning and just after noon. Its about 150' from the other one and both locations are on a gradual slope with neither being at the peak or hollow. Right away I noticed the following differences, not counting when the sun hit the old thermometer or that side of the house:

Sunny days - old thermometer was 2-5 degrees higher than new one
Cloudy/rainy days - old thermometer was never more than 2 degrees higher than new one, usually within 1 degree
Clear nights with wind - never more than a degree apart
Clear nights without wind - old thermometer 2-4 degrees higher
Cloudy/rainy nights - never more than a degree apart

I tested this by clipping the new thermometer right next to the old one and for four days the temps moved in lockstep, never differing by more than 0.2 degrees at any time, including daily max and min.

I am wondering if heat radiating from the house has anything to do with the differences, especially given the differences decreased in windy/rainy/cloudy weather. I also tested the old one in shade within 20 feet of the asphalt driveway and the sunny day difference was 4-9 degrees and the clear calm night difference was only 1-2. Makes you wonder just how accurate those airport thermometers next to paved runways, vents and small outbuildings are.

This post has been edited by kpk33x: May 31 2013, 12:31 PM


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Autumn 2017 - Mahomet, IL

First day with...
...Low below 40F:
...Frost:
...First sub-freezing low:
...Snow reported:

Foliage: Some color starting to show (Sept. 14)
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