Desert nights: How low do the temperatures get?

They say temperatures in the Sahara can hit 104, 122, or even higher during the day, only to plummet toward freezing once night falls.

What’s the catch?
Since rock and sand act as decent thermal insulators, you’d think if they soak up that much heat during the day, they’d hold onto it longer and cool down slower, keeping the temperature steady through the night.

Why don't we see those same kinds of extreme temperature swings in the Midwest? The landscape there is somewhat similar to desert dunes—flat plains, and in the spring or after harvest, you just have bare soil and low vegetation without much forest cover to speak of.

Honestly, you’re comparing apples to oranges here.
It’s a fundamental misunderstanding of how thermal dynamics actually work. Take the sand in the Sahara, for instance—it is bone-dry and incredibly light in color. Because that sand is so parched, it doesn't hold onto heat the way damp soil does, and since it's lighter in shade, it absorbs far less solar radiation than darker ground would. Furthermore, we can't ignore the role of water vapor in the atmosphere, which is practically non-existent in the Sahara; that missing moisture is a massive factor because water vapor is what typically helps regulate and maintain ground temperature. Without that humidity to act as a buffer, the desert floor simply loses its heat at an accelerated rate.
Contrast that with the Midwest, where the soil is significantly darker, the earth remains much more hydrated, the air is thicker with humidity, and there is actual vegetation present to trap and hold that warmth within the ground.

Bradley Lewis59 said:You're conflating two completely different concepts here.
The sand in the Sahara is dry and light-colored. Dry sand doesn't retain heat the way moist soil does. Plus, lighter sand absorbs less thermal energy than darker ground. Another major factor is water vapor in the air—which is virtually non-existent in the Sahara. That humidity is what actually keeps ground temperatures stable. Because there’s no moisture in the air out there, the ground cools down much faster.
In the Midwest, the soil is darker, the ground is wetter, the humidity is higher, and you have vegetation that helps trap heat in the earth.

Have you ever actually tried walking barefoot in the Sahara? Sure, it's light-colored, but it's scorching. If it isn't hitting 150F, it isn't even worth mentioning. I ran about 50 feet barefoot once and nearly suffered third-degree burns.🙂
I'm also trying to wrap my head around this, but I can tell you one thing: it definitely isn't because the sand is light-colored and fails to heat up.

So, you’ve got this crazy combo of bone-dry air and parched, thirsty ground. It’s wild because when the soil is that dry, it just can’t hold onto any heat like damp earth does—it’s basically useless at it. Plus, since the air is so incredibly arid, all that warmth just evaporates way faster because there isn't a single cloud in sight to act as a blanket and slow down the whole process.