Another record-breaking heat wave is expected for California, Arizona and Nevada over Labor Day weekend, forecasters said Tuesday.
Even southwest Oregon was under a heat advisory.
"High pressure building in the west will contribute to temperatures being 15-20 degrees above average for much of Oregon by Thursday," the National Weather Service office in Portland said in an urgent weather message Tuesday.
High pressure is expected to park itself over the desert southwest this week and turn on the burners, particularly for Southern California, southern Nevada and southwest Arizona, federal forecasters said. It's expected to last Friday through Monday.
It would be the second stretch of scorching — and record-setting — days in roughly three weeks.
The National Weather Service has issued an excessive heat watch Friday through Monday for San Diego County, Orange County, Los Angeles County, the Inland Empire, Las Vegas, and Phoenix. For the Bay Area the watch covers Saturday through Monday.
"This has potential to be a very dangerous heat wave," said meteorologist Todd Hall of the National Weather Service's office in Oxnard, California, adding that the heat could hang around until Wednesday.
For the more than 20 million inhabitants of Southern California, the worst of the heat is expected Sunday, he said.
"We’re going to be near record all-time heat," Hall said.
Sunday's high temperature for Burbank, in Los Angeles County's San Fernando Valley, is forecast to be 111, just a digit off from its all-time high of 112, recorded July 22, 2006, Hall said. Woodland Hills is expected to reach 115, he said.
The last time high and overnight temperatures broke records was mid-August, when triple-digit heat up and down the state was accompanied by dozens of wildfires, two of which became the second- and third-largest fires in state history.
The 391,150-acre SCU Lightning Complex Fire, named for the California Department of Forestry and Fire Protection's Santa Clara Unit, and the 375,209-acre LNU Lightning Complex Fire, named for Cal Fire's Sonoma-Lake-Napa Unit, are still technically active.
The agency reported containment for each was greater than 70 percent Tuesday.
Cal Fire spokesperson Lynne Tolmachoff said comparatively mild weather in recent days has allowed firefighters to make progress on existing fires.
"With this heat coming, any new starts could create problems," she said. "We're staffed up. With the holiday there’s going to be a lot of people out recreating. We’re asking people to stay safe and don’t start new fires."
The last heat wave also triggered rolling blackouts throughout the state as California's power grid was overloaded by demand.
On Tuesday, the California Independent System Operator said on Twitter, "While hot weather is forecast statewide Labor Day weekend, it is too early to assess the impacts of heat on grid conditions. No Flex Alerts or Stage Emergencies are planned at this time."