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Old 04-01-2011, 11:50 PM
 
Location: motueka nz
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Today felt like the first real Autumn day (6-19C/42-66F), which got me thinking about sun vs shade temperature. I had 4 thermometers, 2 in the shade and 2 in the sun. They were all suspended at head height above grass. At the warmest part of the day the difference was 19C/66F in the shade vs 31C/90F in the sun. At 5.00 pm it was 18C/64F in the shade vs 20C/69F in the sun.. I had an (accidental) sun reading last summer that was 50C+/122F, although that was on the ground. I would be interested to know what the difference is at different latitudes, and if the difference increases/decreases with the seasons.
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Old 04-02-2011, 05:30 AM
 
Location: Surrey, London commuter belt
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A few years ago in June I put a thermometer on the patio and in full sunlight. It maxed out at 54C, with an air temp of about 33C.
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Old 04-02-2011, 01:39 PM
 
Location: motueka nz
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Quote:
Originally Posted by B1987 View Post
A few years ago in June I put a thermometer on the patio and in full sunlight. It maxed out at 54C, with an air temp of about 33C.
The thermometers I have only read to 50C, so I don't know if the one on the ground got any hotter than that. The day was average, so likely in the mid 20's and the thermometer was on grass. I have tunnel houses which can give 50C readings from Oct-Mar on a sunny day, if I close up the doors,.... something not to be recommended.
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Old 04-02-2011, 04:55 PM
 
Location: USA East Coast
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I saw a National Geographic documentary a few years ago. They said that on the handful of days that Death Valley, CA records temps of the 120 – 122 F (48 – 50 C) inside a shaded instrument shelter…pavement temps in full sun are often closer to 70 C (160 F)…
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Old 04-03-2011, 02:10 PM
 
Location: motueka nz
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Originally Posted by wavehunter007 View Post
I saw a National Geographic documentary a few years ago. They said that on the handful of days that Death Valley, CA records temps of the 120 – 122 F (48 – 50 C) inside a shaded instrument shelter…pavement temps in full sun are often closer to 70 C (160 F)…
So perhaps a 20C difference between sun and shades is the upper limit? Death Valley would be a good place to test that I would think.
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Old 04-03-2011, 02:26 PM
 
Location: Miami, FL
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Hmm I just tried this out right now. With the full sun shining on the pavement I recorded 86 degrees, air temperature is 81. At head level in the shade I got 74
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Old 04-03-2011, 02:27 PM
 
Location: Yorkshire, England
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Originally Posted by Stoney63 View Post
So perhaps a 20C difference between sun and shades is the upper limit? Death Valley would be a good place to test that I would think.
I've forgotten half the physics behind meteorology I once knew but what about mountainous areas, particularly in spring with high sun angle yet still low air temps? I've heard of people sunbathing in 0-5C shade temp, yet the sun still strong enough (and presumably warm enough?) to feel comfortably warm if there's no wind.
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Old 04-03-2011, 09:04 PM
 
Location: Perth, Western Australia
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depends on what your thermometer is made out of, I reckon. (conductor/insulator, colour of housing etc.)
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Old 04-03-2011, 09:42 PM
 
Location: motueka nz
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Originally Posted by ColdCanadian View Post
depends on what your thermometer is made out of, I reckon. (conductor/insulator, colour of housing etc.)
Budget white plastic ones, with only two points of contact(with the housing) along the length of the tube. They are consistent with my pricey digital ones though. I would think these are as good as anything, assuming there isn't such a thing as a sun thermometer. No difference at present ( both at 19C ) due to the rain. Yesterdays max difference that I saw was only 11C.
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Old 04-04-2011, 04:07 AM
 
Location: The western periphery of Terra Australis
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I think you'd need a proper enclosure to test it out, because other factors like the localised wind etc would have to be factored in.
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