Quote Originally Posted by gjl View Post
Official temperatures are always measured in the shade.
Well - sort of. So the Mesonet stations themselves are not in the shade; in fact, to the greatest extent possible, they are all located in an open area away from any obstructions that might prevent accurate wind or rainfall measurements. That said, the temperature sensors themselves are shaded in a device called a Solar Radiation Shield, which is a louvered enclosure designed to prevent sunlight or rain from landing on the temperature probe - while still allowing air to flow freely through the enclosure. This helps to prevent sunlight from influencing temperature readings. Many PWSs come with these shields for their temperature sensors, like the Ambient Weather WS-2902C that I have. However, one BIG difference between mine and the equipment used by the Oklahoma Mesonet or NWS is theirs have small fans to continuously circulate air through the shield - this ensures that you're consistently getting a true reading of actual air temperature. Without it, on bright sunny days with little to no wind, the solar radiation shield can trap warmer air inside and that affects the reading.