Desert Temperatures

How can a place so hot get so cold?  

Recently we received a question from someone who had been camping in the desert. He was curious about the temperature variations.  During the day it can be extremely hot; only to be followed by relatively cold nights.  

Hot during the day and cold at night

Humidity is the key to this phenomenon.  Humidity reflects the suns radiation as it comes in and then helps trap in the heat energy fro leaving. Deserts typically have low humidity.  Because of the clear dry air and minimal vegetation,  a high percentage of the sunlight reaches the ground. The rocks and soil absorb the intense heat.  At night, the ground emits the heat energy it gained during the day back towards space.  Without humidity to trap the heat energy in, the radiation dissipates quickly at night.  The result is relatively cool nights.

Are all deserts the same?  Nope, there are four main classifications.

As a general rule, a desert is a region with sparse vegetation little rainfall.  A desert typically receives less than 19.7 inches (50)cm of rainfall.  Deserts are not limited to hot regions; deserts can be hot or cold.  Cold? Yes, think of Antarctica. Antarctica fits the general description but is not commonly considered a desert.  Realizing the broad definition, it is easy to see how 1/5th of the world is considered a desert.

  1. Arid (Hot and Dry)  -Located in low altitudes with warm temperatures all year and a long with a hot summer.  Winters provide little rain.  The evaporation rate is high.  Many times the  evaporation rate exceeds the rainfall.  Rain can actually evaporate before it hits the ground. Maximum temperatures reach  120°F (49°C) with minimums of 10°F (50°C). Average rainfall is 0.6 in. (1.5cm) but can be as high as 11 in. (28cm) in North American deserts. 

  2. Semiarid - Summers are dry with minimal rain during the winter. Semiarid deserts are not as hot as Arid deserts. The summers bring highs of  100° F (38° C) during the day, but slip to 50°(10°C) degrees at night.  Average rainfall is 1.2 in. (3cm).

  3. Coastal - Located on the western coasts of continents, between 23°N and 23°S, with warm summers and cool winters.  Rainfall averages about  4 in. (11 cm) but can achieve highs of  14 in. (37cm).  Maximum temperatures can reach  95°F (35°C) with minimums of 24.8°F (-4°C). 

  4. Cold - Includes the Arctic, Antarctica, and many parts of the tundra regions.  Summers are short with long cold/rainy/snowy winters.  Average temperatures are 75°F (24°C) in the summer 34°F (1°C) in the minter.   Average rainfall can range from  inches 18in. (46cm) to 4.5 in. (9cm).  In many cases the majority of the precipitation is in the form of snow.