How can deserts get cold at night

When the heat source is taken away, that vapor will retain it for long periods. Humidity is also why deserts can feel hotter than other places even though the temperature is the same.

The water vapor needs lots of solar energy to heat up, while a dry climate takes that energy head-on. All of this happens quickly because of that lack of humidity. Humidity in the air is important to regulate the climate as it can hold and retain heat, unlike sand.

When there is ample humidity in a desert, the vaporised water created an invisible blanket around the surface by trapping heat. High humidity also means more energy required to dissipate the heat. Whereas in non-humid conditions of Sahara, the air cools down very rapidly as there is no humidity to store the heat. If you look closely, Saharan plants and animals have different adaptations than other desert dwellers. But, at night most of the heat in the sand quickly radiates into the air and there is no sunlight to reheat it, leaving the sand and its surroundings colder than before.

However, this phenomenon alone doesn't account for such a drastic drop in temperature. After all, when the sun goes down on a tropical beach, you don't need to don a winter coat.

The main reason for the stark temperature change is that desert air is extremely dry. In arid deserts like the Sahara and the Atacama Desert in Chile, the humidity — the amount of water vapor in the air — is practically zero, and unlike sand, water has a huge capacity to store heat.

Water vapor in the air traps heat close to the ground like a giant invisible blanket and stops it from dissipating into the atmosphere, according to World Atlas. Air with high humidity also requires more energy to heat up, meaning it also takes more time for that energy to dissipate and for the surroundings to cool down. Therefore, a lack of humidity in deserts allows these arid places to quickly heat up but also rapidly cool. Despite these rapid temperature swings, desert animals are well adapted for the desert's extreme temperature changes.

Reptiles, the most abundant and diverse animal group in the desert, are well adapted to extreme temperature variation because they are cold blooded, or ectothermic, which means they do not need to invest energy in maintaining a constant body temperature. In other words, reptiles can use this energy elsewhere, like hunting.

Once the sun sets, there is no heat to either absorb or hold on the surface. However, there is also no Sun in other parts of our planet, but the temperatures do not vary so greatly between night and day. Why does this happen only in the desert?

The lack of humidity is the main reason. Humidity is what helps heat to remain in the air during the night. This happens in a lot of other tropical places.

In the simplest terms, humidity is water that is suspended in the air. More humid air has larger amounts of water in it; it is simple. Water is able to hold heat much better than air itself.

This is why in places with higher humidity , the air can hold heat for longer periods than in places with lower humidity. The air is not what is actually holding the heat, but the water in it.