Extreme and prolonged heat waves have engulfed much of Britain and Europe in recent weeks, and now Canada and the United States are facing their turns, with temperatures set to soar to record-breaking levels for millions of people this week.
It’s enough to wonder: Are they connected?
While the extreme heat in Europe isn’t traveling across the Atlantic to directly set off the heat waves in the United States and Canada, the events are intimately linked through the same global atmospheric patterns.
Here’s how that works.
How heat domes work
The immediate culprit behind all these days of extreme heat is the development of sprawling, stubborn high pressure systems, also known as heat domes.
Whether they’re sitting over France or Philadelphia, their mechanics are the same. In fact, heat domes occur all over the world.
Like a lid on a boiling pot, they trap and “cook” the air beneath them. Warm air is then pushed down toward the ground, and as it sinks, it compresses and becomes significantly hotter.
Heat domes can also linger for days, and sometimes even weeks. They also suppress cloud formation, block rainfall and prevent cooler air from moving in, so with a constant supply of sunshine and hot air, regions trapped beneath a heat dome can quickly reach dangerously high temperatures.
Blame the jet stream, a little.
Part of a heat dome’s stubbornness can be linked to the jet stream — a fast-moving ribbon of air, high up in the atmosphere that circles the globe from west to east, driving a conveyor belt of weather systems at ground level.
In the Northern Hemisphere, the jet stream exists because of the temperature difference between the Equator and the poles, according to the Met Office, Britain’s weather service. Cold polar air lies to the north of the jet stream, while warmer tropical air lies to the south, and it is this temperature gradient that drives the winds.
Often the jet stream winds follow a relatively straight path, but it can also meander and buckle. When this happens, weather systems slow down, sometimes allowing areas of high pressure or heat domes to develop and dominate. In simple terms, this is how these heat domes over Europe and the United States have formed.
While tying a single heat wave to climate change requires extensive analysis, scientists have no doubt that heat waves around the world are becoming hotter, more frequent and longer lasting, and Europe is warming faster than any other continent.
The past 11 years have been the hottest on record. The World Meteorological Organization confirmed in March 2025 that 2024 was the hottest year and the first year in which Earth’s surface was more than 1.5 degrees Celsius above its average during the preindustrial era.
The bouts of exceptional warmth are driven in large part by the continued emissions of heat-trapping gases, mainly from the burning of fossil fuels.
