No Storm Sirens, No Warnings You Can See — Why Heat Domes Are America's Most Underestimated Killer

When a heat dome forms over a region, temperatures can climb to dangerous levels for days or even weeks at a time — and the threat is not limited to summer. Heat domes can develop in any season, catching residents off guard before they have had a chance to prepare. Understanding what a heat dome 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.