What is a heat dome? A meteorologist explains the weather phenomenon baking large parts of the US

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William Gallus, Iowa State University

(THE CONVERSATION) Heat domes, which have sent temperatures soaring in the U.S. in 2024 and roasted large parts of Europe during the Paris Olympics, occur when a persistent region of high pressure traps heat over an area. A heat dome can linger for days to weeks, leaving the people, crops and animals below to suffer through stagnant, hot air that can feel like an oven.

Typically, heat domes are tied to the behavior of the jet stream, a band of fast winds high in the atmosphere that generally runs west to east.

Normally, the jet stream has a wavelike pattern, meandering north and then south and then north again. When these meanders in the jet stream become bigger, they move slower and can become stationary. That’s when heat domes can occur.

When the jet stream swings far to the north, air piles up and sinks. The air warms as it sinks, and the sinking air also keeps skies clear since it lowers humidity. That allows the sun to create hotter and hotter conditions near the ground.

If the air near the ground passes over mountains and descends, it can warm even more. This downslope...