At night, deserts are often very cold. The temperature drops steeply in the evening because there are no clouds to keep in the day's heat. Some deserts in central Asia are cold even by day. So desert creatures must be able to cope with cold, as well as heat. Dwarf hamsters, of Mongolia, have thick fur, which they fluff out to keep warm at night. Bactrian camels grow thick fur for the winter, and molt again in spring.