When you think of deserts, you probably think of excessive heat accompanied by sweat and exhaustions and heat-strokes. If you’re someone who has never lived or spent much time in a desert, it might be surprising to know that deserts actually get quite cold at night. The Sahara Desert in Africa has extreme temperature variations between day and night can. For instance, the Saharan temperature during the day can be 38-degree Celsius high, but at night it can be as low as -4 degree. However, not all deserts have variations this extreme.
Two conditions contribute to this change: heat and humidity. One of the reasons behind this drastic change is hidden in the grains of sand covering the desert. Sand gets hot really fast; so, when the sun is shining bright, it absorbs all the heat directed at the surface. The light substance is also great at reflecting the heat into the surrounding air, making it super-hot.
But it cannot retain it. Once the rays of the sun stop hitting the surface, all the heat in the top sandy layer gets released into the air. Once the top layer is cooled down, and no source of heat remains in the air, the subsequent layers of air also start getting colder. So, if you are in a tropical desert, there will be a sharp drop in temperature but you will not be freezing. But in deserts like Sahara (or other arid deserts like the Atacama in Chile), there is little to absolutely no humidity in the air. 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. More energy=slower cooling down. 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.
The cold-blooded reptiles here are smaller; so, they can find warm nooks at night or cool shades during day. Camels, who are warm-blooded, have a form of fat and thick fur—this way they don’t heat up too much during day and don’t freeze at night. Birds here use ‘evaporative cooling’ by using water to transfer heat away.
Plants, which are more susceptible to freezing, simply avoid growing in areas with below-zero night temperatures.