Heat dome kills at least 500 people across Canada, Oregon and Washington as temps reach 118F – hotter than Death Valley

The heatwave was caused by what meteorologists described as a dome of high pressure over the Northwest and worsened by human-caused climate change, which is making such extreme weather events more likely and more intense.

Amid the dangerous heat and drought that is gripping the American West, crews were closely monitoring wildfires that can explode in the intense weather.

In Lytton, British Columbia, there were several reports of buildings on fire on Wednesday after the region recorded Canada's highest-ever temperature for three days in a row.

While the temperatures had cooled considerably in western Washington, Oregon, and British Columbia by Wednesday, the interior regions were still sweating through triple-digit temperatures as the weather system moved east.

The government's Environment Canada agency issued heat warnings Wednesday for the provinces of southern Alberta and Saskatchewan. 

Heat warnings also were in place for parts of states such as Washington, Oregon, Idaho, and Montana.

In Alberta, "a prolonged, dangerous, and historic heatwave will persist through this week," Environment Canada said in a release.

The very high temperatures or humidity conditions also were expected to pose an elevated risk of heat stroke or heat exhaustion.

Officials in Bremerton, Washington, said heat may have contributed to four deaths in that Puget Sound city.

The death of a worker at an Oregon plant nursery last weekend was heat-related, employee safety agency Oregon Occupational Safety and Health Administration said on Tuesday.

The man was from Guatemala and had apparently arrived in the U.S. only a few months ago, said Andres Pablo Lucas, owner of Brother Farm Labor Contractor that sent the man and other workers to the nursery.

The man, whose name was not released, died amid sweltering temperatures Saturday at Ernst Nursery and Farms, a wholesale supplier in St Paul, 20 miles north of the capital of Salem.

Speaking in Spanish, Pablo Lucas said that when workers gathered shortly afternoon on Saturday, they noticed someone was missing. 

They began searching and found his body. Pablo Lucas said he didn't remember the man's name.

The laborers often have the option to start working around sunrise when it is cooler and can stop around midday, but some want to stay regardless of the heat, Pablo Lucas said.

"The people want to work, to fight to succeed. For that reason, they stay," he said.

The United Farm Workers urged Washington Gov Jay Inslee to issue emergency heat standards protecting all farm and other outdoor workers in the state with a strong agricultural sector.

In western Washington, the heat led a utility in Spokane to impose rolling blackouts because of the strain on the electrical grid. 

About 9,300 Avista Utilities customers lost power on Monday, and the company said more planned blackouts began on Tuesday in the western Washington city of about 220,000 people.

"We try to limit outages to one hour per customer," said Heather Rosentrater, an Avista vice president for energy delivery.

She said the outages were a distribution problem and did not stem from a lack of electricity in the system.