Scientists Say: Heat dome

AhmadJunaidTechnologyJuly 7, 2025361 Views

Heat dome (noun, “HEET DOHM”)

A heat dome occurs when hot weather stalls over an area for days or weeks at a time. It forms when warm air at Earth’s surface gets trapped and cannot rise. Heat domes can cause periods of unusually hot weather called heat waves.

In the atmosphere, warm air typically rises and cool air sinks. Air near Earth’s surface heats up, causing it to rise. As warmed air rises, it begins to cool and sink down again. This hot-cool cycle helps keep air moving in our atmosphere.

A heat dome forms when heated surface air cannot rise. This can happen when a zone of high-pressure air moves over an area. High pressure is a region of sinking air high in the atmosphere. It’s usually marked by sunny skies and few clouds.

Sometimes, high-pressure air can prevent surface air from rising and cooling. Since this air remains near the Earth’s surface, it keeps getting hotter and forms a heat dome. The heat dome also blocks other weather from entering the region, including clouds and rain. As the region becomes drier, temperatures soar higher.

Warm air in a heat dome isn’t just blocked from rising. It often cannot move out of the region, either. In North America, weather tends to move from west to east. But changes in the jet stream — a fast-moving air current high in the atmosphere — can block this motion. Such roadblocks can trap a high-pressure system for days or even weeks. This also can contribute to the formation of a heat dome.

Heat domes’ high temperatures and dry conditions can increase the risk of wildfires. They bring other problems, too. In cool and mild regions, heat domes can cause unusually hot weather. Extreme temperatures may be especially dangerous to people living in such areas. That’s because they may lack air conditioners or other tools for managing the weather.

As the Earth’s climate changes, heat domes — and the extreme temperatures that come with them — become more common.