The western United States and Canada are bracing for a record-breaking heat dome this weekend, with temperatures expected to soar to the summer's highest levels yet. A massive area stretching from southern California to western Canada will be affected, with tens of millions of people under heat alerts.
The heat dome, caused by a high-pressure system that traps and enhances hot air beneath it, will bring temperatures 12 to 24 degrees Celsius above normal, even for the peak of summer. Death Valley, California, is forecast to see the hottest temperature, a blistering 52 degrees Celsius. This is the latest in a series of record-breaking heat waves that have affected the region this summer.
Researchers are exploring whether strong and slow-moving heat domes are becoming more common as the world warms. Heat domes work by acting like a lid on a pot, trapping hot air beneath them and raising the ceiling on surface temperatures. This heat dome is expected to reach even higher in the atmosphere than typical, making it especially extreme.
More than 12 million people across the Southwest, Mountain West, and northern Great Plains are under an "extreme" heat risk, with an additional 12 million people under a "major" heat risk. The National Weather Service warns that heat at this level will affect anyone without access to cooling and hydration.
By Tuesday, around 10% of the continental United States will record the hottest day of the year so far, with more hot weather predicted in large parts of the West beginning on Thursday. Overnight lows will also remain nearly 10 degrees above normal, giving the body less time to recover before the next day's heat.
