Optimal thermometer placement

Dear Tom,
What is the proper placement for the sensor element for a wireless
thermometer? Mine, located on the house above the patio, reads much hotter
than the reported temperature. Is there a general rule to follow when
selecting a location?
Fred Kloster, Naperville
Dear Fred,
Proper thermometer placement is not easily accomplished in an urban
environment.
The temperature-sensing element must be protected from exposure to direct
sunlight, from precipitation (like rain) and from condensation (like dew),
while at the same time be given adequate ventilation. It must also be
located well away from mechanical heat sources (such as air conditioners)
and from concrete surfaces that are warmed by sunlight.
Ideally, the sensor is best placed in a wooden instrument shelter with
louvered sides, painted white, four feet off the ground, over grass.