Western states in the US are continuing to endure scorching hot temperatures, with heat warnings in place and authorities battling to contain wildfires in both the US and neighbouring Canada.

The so-called ‘Bootleg Fire’ in Oregon had burned more than 143,000 acres in the southwest of the state as of Sunday evening, as officials warned of continued “dangerous and rapid growth”.

The National Weather Service in Medford said on Sunday that the fire had doubled in size every day for the past three days, leaving California’s electricity supply at risk and forcing officials to order the evacuation of at least hundreds of residents.

By Sunday night, more than 900 firefighters were battling the fire, which isn’t expected to be contained until July 27.

Across parts of Klamath County, level three – “go now” – evacuations were ordered.

The Klamath County Sheriff’s Office has started issuing citations and said it would make arrests to keep people out of those evacuation areas.

The fire started on Tuesday afternoon about 15 miles northwest of Beatty, and persisted under hot, dry and windy weather in the area, Fremont-Winema National Forest officials said. The cause remains under investigation.

The weather, as well as “extremely dry fuels” following a persistent drought, contributed to “extreme” fire behaviour, officials said. Conditions had escalated on Saturday, forcing firefighters to retreat to predetermined safety zones, officials said.

The fire has been totally uncontained since Friday.

Emergency officials said seven uncontained wildfires were burning across the Pacific Northwest, including the Bootleg Fire, as of Sunday.

The total burn area of those fires was about 210,000 acres.

In northern California, many areas were under an excessive heat warning.

The California Independent System Operator, which manages electricity for a power grid that serves 80pc of California, warned that the Bootleg Fire had made transmission lines from Oregon “unreliable”.

The heatwave was forecast by the US National Weather Service to keep its grip on much of the West through to at least today.  

The latest heatwave comes after the Pacific Northwest endured a deadly “heat dome” late last month. The death toll from that event in Oregon alone stands at 116 fatalities.

The fatal event was “virtually impossible” without climate change, scientists found.

© Washington Post