Think of a desert. You probably just imagined a scene from a cartoon—shimmering heat waves, a bleached cow skull, and maybe a lone cactus. It's hot. Obviously. But if you actually spent a week in the Sahara or the Atacama, you’d realize that the climate of a desert is way more schizophrenic than the movies suggest.
It’s brutal.
One minute you’re sweating through your shirt, and twelve hours later, you’re shivering in a down jacket because the temperature plummeted forty degrees the moment the sun dipped below the horizon. Most people think deserts are defined by heat. They aren't. Deserts are defined by dryness, or more specifically, a massive deficit in precipitation.
The Atacama Desert in Chile is the perfect example of this weirdness. In some parts of the Atacama, it hasn't rained in recorded history. Not a drop. Yet, it isn't always scorching; because it’s at a high altitude, it can be downright chilly. This is the reality of the climate of a desert: it’s a world of extremes where water, or the lack of it, dictates every single biological and geological rule.
The Aridity Myth: It’s Not Just About the Heat
To get why the climate of a desert works the way it does, you have to look at the "B" group in the Köppen climate classification system. Meteorologists don't just lump all dry places together. You’ve got your "BWh" (hot desert) and "BWk" (cold desert).
The Gobi Desert in Mongolia is a "BWk" classic. It’s a desert, sure, but in the winter? It’s a frozen wasteland. We’re talking -40 degrees. That’s because the climate of a desert is driven by atmospheric pressure and geography, not just how close you are to the equator.
Why is it so dry?
Usually, it’s one of three things. First, you have the subtropical high-pressure belts. Around 30 degrees north and south of the equator, air sinks. When air sinks, it warms up and stays dry, which basically kills any chance of rain. This is why the Sahara exists.
Then there’s the rain shadow effect. Imagine a massive mountain range. Clouds hit one side, dump all their rain, and by the time the air gets over the top to the other side, it’s bone dry. Death Valley lives in the shadow of the Sierra Nevada. It's a geographical trap.
Lastly, you have continentality. Some places are just too far from the ocean. By the time a moist breeze from the Atlantic tries to reach the middle of Asia, it’s out of gas.
The Nighttime Freeze: Where Did the Heat Go?
This is the part that messes with travelers the most. You expect to be hot. You don’t expect to see your breath at 2 AM.
In a humid environment—like a jungle or even a typical backyard in Ohio—the air is full of water vapor. Water is incredible at holding onto heat. It acts like a giant, invisible thermal blanket. During the day, the ground gets hot, and at night, that humidity traps the heat near the surface.
In the climate of a desert, that blanket is missing.
The air is so dry that the heat absorbed by the sand during the day just radiates straight back into space the second the sun disappears. There’s nothing to stop it. This is why the Sahara can hit 120°F (49°C) during the day and drop to 30°F (-1°C) at night. It’s an atmospheric "fast-forward" button for temperature changes.
If you're planning a trip to a place like Joshua Tree or the Wadi Rum, honestly, pack layers. You'll feel like a fool carrying a fleece when it's noon and the sun is trying to melt your brain, but you’ll be the only one not miserable once the stars come out.
Survival is a Game of Evaporation
Let’s talk about "Potential Evapotranspiration." It sounds like a boring lab term, but it’s the heartbeat of desert life. Basically, it’s a measurement of how much water would evaporate if there were actually water there to begin with.
In a desert climate, the potential evaporation is always much higher than the actual rainfall.
Take the Sonoran Desert. It actually gets a decent amount of rain compared to the Sahara—sometimes up to 12 inches a year. But because the sun is so intense and the air is so thirsty, that water vanishes almost instantly.
Plants have to be geniuses to survive this. The Saguaro cactus is basically a giant living water tank. It has an accordion-like skin that expands when it rains so it can soak up every drop. It doesn't have leaves because leaves lose water. It has spines. Spines don’t just protect it from thirsty bighorn sheep; they actually provide a tiny bit of shade to the cactus’s skin and break up the wind, which slows down evaporation.
Real Talk: The Most Famous Deserts Aren't What You Think
We tend to generalize, but the climate of a desert varies wildly depending on where you are on the map.
- The Sahara: The king of hot deserts. It’s roughly the size of the United States. It’s mostly rocks and gravel (regs), not just sand dunes (ergs), contrary to every movie poster ever.
- The Namib: This one is weird. It’s a "coastal desert." It sits right on the Atlantic Ocean in Africa. Because of the cold Benguela Current, the air is cool but carries no moisture. Instead of rain, the Namib gets thick, eerie fog. The beetles there literally stand on their heads to let the fog condense on their backs so they can drink the drops.
- Antarctica: Yes, it’s a desert. It’s the largest desert on Earth. It gets almost no snow, and it's the driest, windiest place on the planet. It’s a "polar desert."
Human Impact and the "Green Wall"
The climate of a desert isn't static. It moves.
Desertification is a massive issue right now, specifically in the Sahel region of Africa. This is the transition zone between the Sahara and the savannas. Because of overgrazing and shifting weather patterns, the desert is effectively "leaking" southward.
To fight this, dozens of countries are working on the "Great Green Wall," a massive project to plant a line of trees across the entire width of Africa. The goal isn't just to stop the sand; it's to change the local microclimate. Trees hold moisture in the soil and transpire water into the air, which can actually encourage more localized rainfall. It’s a bold attempt to hack the climate.
Practical Insights for the Desert Bound
If you're heading into a desert environment—whether for a hike in Zion or a trek in Morocco—you need to respect the physics of the air.
- Cotton is actually okay here. Normally, hikers say "cotton kills" because it stays wet and makes you cold. But in the dry climate of a desert, cotton helps slow down the evaporation of your sweat, which actually keeps you cooler for longer.
- Hydrate before you're thirsty. By the time you feel thirsty in the desert, you’re already behind. The air is literally sucking moisture out of your skin and lungs with every breath. You might not even realize you're sweating because it evaporates so fast.
- Flash floods are a real threat. It sounds insane, but more people drown in the desert than die of thirst. The ground is often hard-packed and sun-baked, so when a rare thunderstorm hits, the water doesn't soak in. It runs off instantly, filling dry creek beds (arroyos) with a wall of water in seconds. Never camp in a wash.
The climate of a desert is a masterclass in balance. It’s a place where life exists on a knife’s edge, governed by the brutal simplicity of heat and the absence of water. Understanding it isn't just about knowing it's "dry"—it's about understanding how the very atmosphere behaves when the water is gone.
Actionable Next Steps:
- Check the Dew Point: When traveling to a desert, look at the dew point on your weather app, not just the temperature. If the dew point is below 30°F, expect a massive temperature drop at night.
- Electrolyte Balance: Don't just chug plain water. In high-heat desert environments, you’ll lose salt rapidly through invisible sweat. Mix in electrolytes to prevent hyponatremia.
- Vehicle Prep: If driving through remote desert regions (like the Australian Outback or the American Southwest), carry at least five gallons of extra water and check your tire pressure; extreme heat can cause tires to over-inflate and blowout.