California cities reported record temperatures this weekend as a punishing and dangerous heat wave only worsened in some areas Sunday.

The heat has already sparked damaging wildfires and stressed the state’s power grid. Forecasters warn the sweltering temperatures also pose health risks as people celebrate the holiday weekend.

The northern half of the West Coast has been spared the worst of the heat wave, according to Sunday excessive heat warnings and heat advisories from the National Weather Service. Most of California and Nevada and parts of Arizona, Utah, Oregon and Idaho should brace for high temperatures, forecasters say.

Meanwhile, two dangerous wildfires are burning through the same California county, creating new challenges for firefighters.

The wind-driven Mill Fire, which started Friday about 250 miles north of San Francisco, has destroyed more than 100 homes in the small town of Weed, blazing through more than 4,200 acres and standing at 40% contained as of Sunday evening, according to Cal Fire.

Siskiyou County Sheriff Jeremiah Larue confirmed two deaths on Sunday afternoon. “There’s no easy way of putting it,” he said before calling for a moment of silence.

The nearby Mountain Fire, close to the small community of Gazelle, meanwhile, grew Sunday evening to nearly 9,000 acres. It was 10% contained, according to Cal Fire.

How hot will it get Labor Day weekend?

The high temperatures are expected to continue in the Western U.S. through the holiday weekend and into the middle of the week – particularly in The Golden State.

Monday’s forecast called for Sacramento to hit a stifling 112 degrees, with Los Angeles at 98 and San Diego at 90. Fresno, Palm Springs and Redding will be well into the triple digits, as well, according to the weather service.

Then there’s Death Valley, which is forecast for 120-plus through Thursday.

“Highs in California will likely threaten monthly temperature records and be particularly dangerous for vulnerable residents,” the Weather Service said Sunday.

Some cities have already seen daily record-breaking highs Sunday:

  • Long Beach checked in at 108 degrees, topping the previous daily record of 107 set in 1988.
  • Camarillo reached 103, exceeding its previous daily record, set in 1961, by 10 degrees.
  • Oxnard hit 101, breaking its daily record of 96 set in 1961.

As coastal cities see record heat, hotter inland communities face mounting risk from the weather.

“Interior Northern California is now heading for a truly dangerous, searing heat wave,” Daniel Swain, a climate scientist at the University of California, Los Angeles, tweeted Sunday. “All-time September records are now all but guaranteed in the Central Valley (on multiple consecutive days!), and all-time (any month) records now appear well within reach.”