Heat domes cause heat waves, Zachary Labe, a climate scientist at Climate Central, told the Associated Press. He described them as high-pressure systems associated with very dry, sunny conditions that trap heat at the surface and help amplify it over multiple days.
The high-pressure dome acts like a lid on the atmosphere, preventing warm air from rising, according to NOAA. Without lift, there is little convection and minimal chances for rain, the agency explained through Fox Weather. The trapped heat builds under dry, sunny skies.
When a heat dome forms over a large land area, it can create a feedback loop: high pressure means dry weather, and because there is little rain or wind, the heat continues to accumulate, according to PBS North Carolina. The extent of the early-summer heat dome over the United States this year has been described as remarkable.
The systems can cover a large geographical area and challenge or break historical temperature records, climate experts said. Heat domes maximize heating by allowing sunlight to penetrate to the Earth’s surface.