Not many people know that temperatures in the Sahara Desert can drop by an average of up to 24 degrees Celsius overnight.
If you are planning a day trip to the Sahara Desert in North Africa, you will want to bring plenty of water and sunscreen. However, if you intend to stay overnight, you should also pack a snug sleeping bag to keep warm.
The reason for this is that the temperature in the Sahara can drop dramatically when the sun sets, from an average high of 38 degrees Celsius during the day to an average low of minus 4 degrees Celsius at night.
The question arises as to why such a significant temperature change occurs in dry deserts like the Sahara. How do native plants and animals cope with such rapid temperature fluctuations?
The reason these arid deserts, which account for about 35% of the Earth’s surface, become extremely hot and then extremely cold, is due to a combination of two main factors: sand and humidity.
According to a 2008 report from NASA’s Jet Propulsion Laboratory in Pasadena, California, when the heat and light from the sun hit the sandy desert, the topmost sand particles absorb heat and release it back into the atmosphere.
During the day, the solar energy radiation from the sand heats the air and causes temperatures to rise. However, at night, most of the heat in the sand quickly dissipates into the air, and without sunlight to warm it, the sand and surrounding environment become colder than before.
However, this phenomenon alone does not explain the severe temperature drop. The primary reason for the drastic temperature changes is the air in the desert is very dry. In arid deserts like the Sahara and the Atacama Desert in Chile, humidity—the amount of water vapor in the air—is effectively zero, and unlike sand, water has a high capacity for storing heat.
Water vapor in the air retains heat close to the ground like an enormous invisible blanket, preventing it from dissipating into the atmosphere. Humid air also requires more energy to heat up, which means it takes longer for that energy to dissipate, and the surrounding environment cools down. Therefore, the lack of humidity in deserts allows these arid regions to heat up quickly but also cool down rapidly.
Despite such rapid temperature changes, desert animals are well adapted to the extreme temperature fluctuations.
“The biggest challenge is finding enough food and water to survive,” said Dale DeNardo, an environmental physiologist at Arizona State University who specializes in desert animals.
Sand and humidity are the main reasons for the significant temperature differences in the desert between day and night.
Reptiles are known to be the most abundant and diverse group of animals in the desert, well adapted to the harsh temperature changes since they are cold-blooded, meaning they do not need to expend energy to maintain a stable body temperature. Many species of reptiles also benefit from being small, which allows them to find cool spots during the day or warmer rocks at night.
However, warm-blooded mammals or larger animals like camels are too large to escape the sunlight and cannot allow their body temperature to drop. Instead, camels survive by maintaining a stable body temperature in both hot and cold conditions. They achieve this by having multiple layers of insulation in the form of fat and thick fur, which helps them avoid absorbing too much heat during the day and losing too much at night.
In contrast, desert birds utilize evaporative cooling methods—they use water to transfer heat away from their bodies, similar to how humans sweat and dogs pant—through a variety of methods (some vulture species urinate on their legs to cool down).
Plants are more vulnerable to extreme temperatures and face a much greater challenge because they cannot move. This is why iconic desert plants like cacti have developed a range of defensive measures, such as spines and toxins, to protect their precious water supply from predators.
However, freezing temperatures at night can kill plants because the water freezes and expands within their tissues, causing irreversible damage. Therefore, plants only grow in areas where the air temperature does not drop below freezing for more than a few hours each night, known as frost-free zones.
