Although our weather thermometer is mounted on the north side of the building and under the eave, it often reads too high, especially on sunny afternoons.
I believe this is due to a cliff we have only about 20 feet from the building. This cliff consists of exposed rocks that I believe absorb the daytime sun and radiate this heat back to the thermometer.
Having no other suitable place to put the thermometer, I guess we'll just have to live with that.