Lisa Pfankuche, age 10; of Kansas City, Missouri, for her question:

What makes a hot desert cold at night?

A hot desert is a dazzling place where the daytime sun beams down from a clear, blue sky. There are a few storms and sometimes a few small clouds, but not enough to make cool shadows. There is nothing to stop the sunbeams from coming down and scorching the ground. The daytime desert gets hot and still hotter as long as the sun shines up above.

But the cloudless sky that lets in the daytime heat, also lets the heat escape after sunset. Clouds and hazy skies prevent the heat of the day from escaping from the ground. Where skies are cloudy, we get hot summer nights. There are few if any clouds to blanket the desert and hold in the. heat of the day. So after the sun goes down, the ground cools fast and the desert air turns chilly, even in the middle of the summer.