California is bracing for the most powerful gusts of the 2020 fire season, raising the threat of more blazes and blackouts this weekend in a region that’s already seen a record 4.1 million acres scorched this year.

A storm coming off the Pacific into Oregon and Washington will push winds over the Sierra Nevada, where gusts could reach up to 70 mph in canyons and atop ridges on Sunday and Monday, according to the National Weather Service.

“This looks to be the strongest event of the year, so far,” the weather service said. “Extreme caution should be taken to prevent new fire starts.”

It raises the prospect that PG&E Corp., the state’s biggest utility, could again shut power on Saturday or Sunday to prevent live wires from sparking blazes, after cutting service earlier this week to about 37,000 customers, or about 96,000 people.

Much of the U.S. West is under threat from wildfires as dry weather and stiff winds have turned hillsides, forests and scrub land into tinderboxes. In California, blazes this year have killed 31 people and destroyed more than 9,200 homes and businesses. In Utah, a utility is warning it may cut power to avoid fires. And in Colorado, officials closed Rocky Mountain National Park as firefighters battle nearby flames.

Winds ahead of this weekend’s Pacific storm will bring some dangers to Colorado and Utah on Saturday before rain and snow sweep the region on Sunday, potentially bringing down the curtain on the worst of the fire season there, said Dave Houk, a meteorologist with AccuWeather.com. “This may actually, more or less, put an end to the Colorado fire season,” Houk said. “That is being a little optimistic, but certainly it will be better going forward.”

In Utah, the arid weather has prompted Rocky Mountain Power to warn it may cut power to about 1,800 customers in Sundance and Summit Park.

In California, if PG&E does cut power again, it would be as early as Sunday and the blackouts could be more widespread than the current outages, according to post on its website Thursday.

“Sunday, Monday and Tuesday — that is when the fire risk is really going to be enhanced, especially across Northern California,” said Jim Rouiller, lead meteorologist with the Energy Weather Group. “That is the target area.”

PG&E has already turned off the power three times this autumn during dry, windy conditions when tree branches can blow into power lines and start a blaze. The next event could affect parts of the San Francisco Bay Area and the Sierra Nevada foothills, the company said.