This year, millions of visitors will be driving west to experience the wide open space of the west. Many will come through the western deserts. There the summer days are hot, scorching hot, and then the sun sets and suddenly, quite suddenly, the desert air is cool and freshly fragrant.

This sudden change happens because the desert air is dry and the bright blue sky is usually free of clouds, In most places, the clouds and fuzzy hazes in the sky act like blankets. They keep the day s heat from escaping from the earth all through the night. The desert has no such cloudy blankets and the day's heat escapes soon after sunset, This is why the desert is so cool, even after a scorching summer's day.