Deserts have very little rainfall in a year--usually less than 10 inches (25 cm). Because there is very little moisture in the air to hold onto the heat from the hot days, desert nights tend to be very cold. Taken together, the extreme temperature fluctuations and lack of water make the desert environment a very harsh one in which to live. The plants and animals you will find there have a wide variety of special features that allow them to cope with desert conditions.