Topics Earth, weather and climate

Why is Death Valley so hot?

Death Valley is so hot because several things stack up in one place. It sits in the desert belt of the Southwest, where the sun is high and the air is dry. It is a long, narrow basin walled in by tall mountain ranges, and those ranges wring moisture out of storms before they arrive. Air that descends from the high mountains into the basin warms as it is compressed, which may add to the heat as one contributing factor. Pale, bare, dry ground soaks up the sun, and with almost no moisture to evaporate, nearly all that energy goes into heating the surface and the air above it.

The depth of the valley is often given as the cause, since the floor lies below sea level. That is a bit misleading. Being below sea level is not itself what heats the air; what matters is the shape of the basin, the descending air and the dry surface. Heat records there are also debated. The famous 1913 reading is currently recognized by the World Meteorological Organization, but some researchers question it.

A bre episode would walk through each cause in turn, then look at why nights stay warm and how the record is argued over. The hosts are AI, so they can be wrong, and you can press Talk to ask a question mid-episode.

What a bre episode would cover

An outline of the episode bre would make for this question. Every episode is written fresh when you ask, so yours will differ.

  1. Sun, latitude and the desert beltWhy this part of the world gets strong sunlight and little rain, and what a subtropical high-pressure zone does to the sky.
  2. The rain shadow of the mountainsHow storms lose their moisture crossing the ranges to the west, leaving the valley dry and clear.
  3. A deep basin that traps heatWhy the valley's long, narrow shape holds hot air in, and why being below sea level is not the real cause.
  4. Sinking air and compressionHow air descending from the high mountains into the basin warms as it is compressed, and why that may add to the heat without being the main cause.
  5. Dry ground and no water to evaporateWhy bare, dry surfaces heat up fast when there is little moisture to carry the energy away.
  6. Warm nights and the heat that lingersWhy the valley cools slowly after dark, with rock and air giving back the day's heat.
  7. The disputed 1913 recordWhat the 134 degree Fahrenheit reading at Furnace Creek claims, why some researchers doubt it, and what is still recognized.

How the episode might open

A sample exchange between two of bre’s AI hosts, bre and Arlo. Both are AI; this is written by AI, as every bre episode is.

  1. breAI host

    Death Valley is among the hottest places on Earth, and it holds a disputed record: 134 degrees Fahrenheit, from 1913. Its summer highs are also often above 110. And the answer to why is not one thing. It's several reasons stacked on top of each other, like blankets on a bed in July.

  2. ArloAI host

    Disputed how? Who counted that?

  3. breAI host

    Fair. Some researchers question the 1913 reading, and we'll get to it in the last chapter. For now, picture the valley: a long, narrow basin with mountain ranges on both sides.

  4. ArloAI host

    Deep hole. Hot hole. Simple.

  5. breAI host

    Not quite, and we'll untangle that. Storms coming from the Pacific have to climb those ranges first, and they drop most of their water on the way up. By the time the air reaches the valley, it's dry.

  6. ArloAI host

    Dry air. So what? Heat's heat.

  7. breAI host

    Okay, here's the part nobody tells you. Sunlight has to go somewhere. When there's wet ground, a lot of it goes into evaporating water. Here there's almost none, so it all goes into heating the rock and the air.

  8. ArloAI host

    Nowhere to spend it. Fair enough. It piles up.

  9. breAI host

    Exactly. And that's before we even talk about air sliding down the mountains and possibly warming as it goes.

Questions people also ask

What is the hottest temperature ever recorded in Death Valley?
The reading of 134 degrees Fahrenheit at Furnace Creek in July 1913 is the figure currently recognized by the World Meteorological Organization as the highest air temperature recorded on Earth. Some researchers question it, so the record is not entirely settled. Summer highs there often exceed 110 degrees.
Does being below sea level make Death Valley hotter?
Not by itself. The heat comes mainly from the desert latitude, dry air, bare ground and the basin's shape. Air that descends from the surrounding high mountains warms as it is compressed, which may add some heat. Depth below sea level is a feature of the place, but it is not what drives the heat.
Why is Death Valley so dry?
Moist air from the Pacific has to rise over several mountain ranges before it reaches the valley. As it rises it cools and drops most of its moisture as rain or snow on the windward, western slopes. This is called a rain shadow, and it leaves dry air on the leeward side, where the valley sits.
Why are nights in Death Valley still warm?
Dry air usually lets heat escape quickly at night, yet the valley's rock and ground store a lot of heat during the day and give it back slowly. The basin's shape may also hold some warm air in. The result is that summer nights can stay far warmer than in most places, though they do cool somewhat.

Related topics

More: all 300 topics, earth, weather and climate, or the longer reads on /learn.

bre’s hosts are AI, and every episode is generated, so they can be wrong: check anything that matters. This page outlines what an episode would cover. It is for interest and learning, not medical, financial or legal advice.