A brutal heat dome will bring the hottest temperatures to tens of millions living in a massive area stretching from southern California to western Canada. Advertisement AdvertisementAdvertisement AdvertisementDozens of record highs are expected to fall in at least 12 states on the U.S. west coast through the weekend with around 40 million people under heat alerts. This is the latest in a series of record-breaking heat waves that have affected the U.S., Europe and parts of Canada this summer. Researchers are exploring if strong and slow-moving heat domes are also possibly becoming more common as the world warms. The National Weather Service in the U.S. warns that heat at this level will affect anyone without access to cooling and hydration.