Heat dome to bring record temperatures across western US and Canada

A powerful heat dome is expected to bring the hottest temperatures of the year to large parts of the western United States and Western Canada, with around 40 million people under heat alerts.

According to CNN, temperatures from southern California to the northern Rockies could rise between 10F and 20F above average from Friday through Tuesday.

Death Valley is forecast to reach 126F, while dozens of daily temperature records could be broken across at least 12 states.

More than 12 million people are under a Level 4 of 4 "extreme" heat risk, with another 12 million under a Level 3 of 4 "major" heat risk, according to the US National Weather Service.

CNN reported that the heat dome is expected to remain in place into next week, with another wave of unusually hot weather forecast from 6 August.

The extreme heat is also increasing the risk of wildfires, placing additional pressure on already strained water supplies across the Colorado River Basin.

Officials warned that overnight temperatures will remain unusually high, offering little relief and increasing the risk of heat-related illness.

According to CNN, heat is the deadliest form of extreme weather in the United States, causing more deaths each year than tornadoes, hurricanes and lightning combined.