Record-breaking heat to test electric grids in western part of the U.S.

Withering temperatures are spreading from western Canada to Mexico this week, setting records across the entire U.S. West as a heat dome sears millions of residents, tests electric grids and threatens to topple an all-time high in Las Vegas.

The city could see record heat Tuesday when temperatures are forecast to hit 118F. There is a 67% chance Las Vegas reached 117F on Sunday, which would tie the all-time high first set in the city in 2005 and 2017, said Jenn Varian, a National Weather Service meteorologist.

“The entire forecast period looks above average, well above average,” Varian said.

High temperatures boost air conditioning use and drive up energy demand. That can impact the electric grid. Wilting heat in recent years has caused disruptions to electricity delivery in California, Texas and across parts of Mexico, risking blackouts. The hot, dry air also elevates the chance of wildfires, which can be devastating.

The heat dome anchored along the U.S. West Coast will drift inland in the coming days, which is driving the pattern, said Frank Pereira, a senior branch forecaster at the U.S. Weather Prediction Center. Through Tuesday across the U.S., 205 daily record highs will be threatened, tied or broken with most of them along the West Coast, but handful in the eastern U.S. where it will also be hot.

As temperatures rise and dry out the land, winds will also start to rise, which means any fires that start threaten to spread out of control.

There will be an elevated risk of wildfires from Oregon to western Colorado with critical conditions breaking out in Idaho today, the U.S. Storm Prediction Center said. There are red flag fire warnings posted across parts of Oregon, Washington and California.