How a heat dome is formed and why experts blame one for Europe's baking temperatures

A heat dome is being blamed for Europe’s early-season baking temperatures, with an early heat wave affecting millions this week. Experts say a heat dome is a stationary high-pressure system that traps dangerous heat and humidity for several days. It forms when a northward bulge in the jet stream alters the weather pattern: sinking air compresses as it descends, raising temperature. Researchers at the Climate Litigation Lab’s Mireia Ginesta and Woodwell Climate Research Center’s Jennifer Francis both described how the jet-stream setup drives the surface heatwave people feel. The situation is most pronounced in France, where about half the country has a red heat alert, and temperatures are expected to reach 40°C (104°F). The national weather service reported around 40 drowning-related fatalities from people seeking cooling relief. Experts link more frequent, intense, and persistent heat domes to climate change, which shifts temperature ranges and raises the odds of extremes.