Firefighters in the western U.S. were facing "critical fire weather conditions," as a rapidly spreading new wildfire in Northern California prompted fresh evacuations Sunday.

Why it matters: Wildfires have burned a record 3.6 million acres in California this year, killing 26 people and razing over 7,600 structures, per Cal Fire. Utility provider Pacific Gas & Electric cut power to 11,000 customers early Sunday and planned outages for 54,000 others later in the day because of fire risks.

Strong offshore winds associated with building high pressure will produce temperatures 15 to 25 degrees above normal across much of the West Coast into this week. Heat Advisories are in effect for the Bay Area in California, and southwestern Oregon. pic.twitter.com/MLlztTRT8I

— National Weather Service (@NWS) September 27, 2020

What's happening: The Glass Fire prompted mandatory evacuation orders for Napa County communities in California's wine country after the blaze broke out Sunday morning and quickly spread across 1,500 acres with 0% containment.

• Red flag warnings were issued "across a large portion of California, the central Rockies and the High Plains," per the National Weather Service (NWS).

The big picture: 69 large fires were burning across the U.S. on Sunday — including 20 in California, 14 in Idaho, 11 in Oregon and 10 in Montana, per the National Interagency Fire Center.

• After cooler, damper conditions earlier in the week, dry and windy conditions were promoting "elevated to critical fire weather conditions across a broad area of the western U.S. into the Plains," the NWS said.

Threat level: Cal Fire noted red flag warnings were in effect until Monday, affecting most areas from Trinity County down through the Diablo Range and Central Sierra Mountains, with low humidity bringing critical fire weather conditions.

• "Gusty winds and low humidity will bring critical fire weather, as well as unseasonably high temperatures," Cal Fire said.
• "A Fire Weather Watch is in effect for later in the weekend into Monday for strong winds and low humidity affecting the Western Klamath in the north and the San Gorgonio Pass and Inland Empire in the south. High pressure brings elevated temperatures across the state through the weekend and into next week."

Editor's note: This article has been updated with the more information on the weather and the fire threat.