Heat Dome

A heat dome is extreme heat trapped by the atmosphere as if under a lid, produced when a strong high-pressure system stalls in place for an extended period and blocks the convection and precipitation that would normally let hot air escape. It typically forms during still, dry summer conditions: a warm air mass builds up, the high pressure above compresses and pushes it back down whenever it tries to rise, and the compression itself further heats the air in a self-reinforcing cycle, while the same system blocks cooling breezes and cloud formation so solar heating continues uninterrupted. The 2021 Pacific Northwest heat dome showed this pattern in a stalled high-pressure system linked to elevated North Pacific sea-surface temperatures, and rising sea-surface temperatures together with human-caused climate change make heat domes more likely.