What Is a Heat Dome and Why Is It So Dangerous?

This week, much of the American Southwest is baking under temperatures that belong in July, not March. The culprit has a name you will keep hearing: a heat dome. Understanding what it is and why it is so dangerous could protect your life the next time one parks over your region.

What exactly is a heat dome?

A heat dome forms when a strong, high-pressure system settles over a large area and essentially acts like a lid on a pot. Warm air that would normally rise and dissipate gets pushed back down toward the surface by the descending pressure. As that air falls, it compresses and heats up further, a process called adiabatic warming. The longer the high-pressure system stays in place, the more intense the heat becomes.

Think of it this way: the atmosphere becomes a sealed greenhouse. There is no mechanism for the trapped heat to escape, and each passing day drives temperatures higher than the day before.