One in five Americans under alerts as heat builds

About one in five Americans - or some 70 million people - are living under heat alerts, with temperatures expected to soar this week.

People in the Northeast and Midwest have been told to prepare for days of extreme heat, with temperatures of 105F (41C) possible in some areas.

Elsewhere in the country, firefighters are battling are wildfire north of Los Angeles that has forced hundreds of people to leave their homes.

Scientists say extreme weather events are becoming more frequent and intense as a result of climate change.

The National Weather Service (NWS) has described this week's expected onslaught as the region's first significant heatwave of the season.

In its latest update on X, it said the Midwest, Great Lakes, Northeast and Mid-Atlantic regions could all be affected through to next week.

"The longevity of dangerous heat forecasted for some locations has not been experienced in decades," its post read.

Thermometers could top 105F and some farming areas could experience drought, the NWS added.

People in the affected areas are advised to limit outdoor activity and stay hydrated.

Temperatures could set a new record for 17 June in Pittsburgh, according to the BBC's US media partner, CBS News. Detroit could endure its hottest day for 12 years.

Across the US in California, a wildfire north of Los Angeles known as the Post Fire has so far burned about 15,000 acres (6,070 hectares) of land.

It is only 2% contained, according to the Cal Fire website. Hundreds of people have been forced to leave their homes.

Earlier this month, daily records were broken during another wave in the Southwest - two weeks before the official start of summer.

Triple-digit readings were logged in locations including Phoenix.