Imagine placing a lid over a pot on the stove. The steam builds, the temperature rises, and everything inside gets hotter and hotter.

That’s essentially what happens in the atmosphere during a heat dome. It’s a sprawling zone of high pressure that traps scorching air underneath it and doesn’t let go.

When a heat dome forms, the air beneath it sinks and compresses, which causes temperatures to soar. The sun beats down day after day with little relief.

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Heat domes can last for several days or even weeks, turning entire regions into ovens. And because they block other weather systems from moving in, there's often no rain to cool things down.

What makes heat domes especially dangerous is that they don't just bring daytime heat – they often prevent nighttime temperatures from dropping too. This lack of overnight relief can strain power grids, dry out vegetation, worsen droughts and take a serious toll on human health, especially in areas where the urban heat island effect amplifies the sweltering heat.

As our climate warms, heat domes are becoming stronger, more frequent and more persistent, making them one of the most extreme types of weather we face.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.