Heat dome triggers record-breaking temperatures across US West Coast

"We're expecting it [the heat] to merely drift east through the early part of next week and basically persist through the week, so we've got a real expansive and extreme heat wave ongoing," Jackson told the news agency.

Another 37 million people across the West Coast are either under heat advisories, meaning they are likely to be affected by extreme heat within the next few hours, or under heat watches, which are issued when a heat event is likely in the next 24 to 72 hours, Reuters reported.