Nicole Merrifield asks: "Why are temperatures measured in the shade?"
In a nutshell, if your thermometer is in direct sunlight, you won't get an accurate reading.
A picture from USA Today shows an extreme example of why. The photo was taken at the National Science Foundation's Summitt Research Camp on Greenland's ice sheet about 10,000 feet above sea level.
The thermometer reads 80 degress. But, if it's 80, why would the man in the picture be wearing a coat?
It's because the actual air itself was in the 20s. The reading of 80 is a reading of the thermometer itself, or the metal around it. The reading is not of the air.
The standard way of reading the air's temperature is in the shade, but that doesn't mean you need to look for a nice shade tree to put your thermometer under.
Instead, there should be an instrument shelter. A common shelter in the U.S. is called a Cotton Region Shelter. It's a white box that reflects sunlight away. The shelters should be placed between four and six feet above the ground.