MUNDANE MYSTERIES: Why Do Hot Deserts Get So Cold At Night?

With it being so warm now, compared to how cold it was just last week, I got to thinking about some other places that experience those temp shifts much more regularly & frequently: deserts. During the day, scorching heat can be torturous to humans. But then, after dark, the problem is reversed & you’d need a winter coat. For instance, temps in the Sahara Desert in Africa can swing a remarkable 75 degrees in just 24 hours, climbing to an average 100°F while the sun’s out, then plummeting to a mere 25°F after the sun sets. But how & why does that happen?

Well, it’s all about the sand, which is an efficient heat distributor when the sun’s out & reflects the warmth back into the air. But, sand’s not so good at retaining heat, so when the sun goes down it lets go of that heat pretty quickly.

Humidity could help retain some of that warm air overnight, but deserts aren’t known to have much humidity. When there’s water vapor in the air, it traps heat. Then, if the heat source gets taken away, that vapor will retain the warmth for a good while. But, without sun or humidity, daytime heat doesn’t get held anywhere, so the desert rapidly cools.

Humidity’s also why deserts often feel hotter than other places even that might have the same temperature. Water vapor needs a lot of solar energy to heat up, but a dry climate just has to take that energy head-on.

Similarly, just as the warm air dissipates when night falls, there’s also no humidity to trap the frigid nighttime weather. So, when the sun rises, it’s back to sizzling.

Now, there are some other factors that can factor in, too: clouds & wind can help moderate & help keep temperatures from dropping. But, overall, you’ll bake in the daytime desert before freezing there at night thanks to the crummy combo of sand and low humidity, which doesn’t make for a consistently comfortable climate. So, if you’ve been thinking about moving to Albuquerque or Timbuktu, it’s probably best if you just keep it right here in Frederick.

Got a Mundane Mystery you’d like solved? Send me a message via social media (@AndyWebbRadioVoice), or shoot me an email at [email protected].

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