Updated on: September 1, 2022 / 12:37 PM / CBS/AP

SAN FRANCISCO -- Laboring will be the optimum word for the upcoming holiday weekend as soaring triple-digit temperatures create challenging conditions for residents, firefighters battling wildfires and air conditioning units powered by the state's overtaxed power grid.

While warnings and alerts from the National Weather Service were already in place in the state's interior and in Southern California, the Bay Area will continue getting a reprieve on Thursday.

But the heat up is on the way as a high pressure dome will settle over the region for the Labor Day weekend.  

The weather service has issued an excessive heat warning starting at 11  a.m. Saturday to 8 p.m. Tuesday for the Sonoma Coastal Range, North Bay Interior Mountains, North Bay Interior Valleys, East Bay Interior Valleys, the Santa Cruz Mountains and Santa Clara Valley.

The remainder of the Bay Area will be under an excessive heat watch.

"We are entering into a period of dangerous heat beginning late this morning for inland portions of the Central Coast and expanding to the remainder of the Bay Area this weekend," the weather service said.

For those planning outside work or Labor Day activities, the weather service warned to stay very aware of the dangerous heat.

"Take extra precautions if you work or spend time outside," the weather service said. "When possible reschedule strenuous activities to early morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear lightweight and loose fitting clothing when possible."

KPIX 5 First Alert Weather: Current Conditions, Forecasts, Alerts For Your Area

Just how hot will it get? The weather service issued a menu of what Mother Nature has in store.

As the heat wave began its grip on the state, Gov. Gavin Newsom declared a state of emergency.

"All of us have been trying to outrun Mother Nature, but it's pretty clear Mother Nature has outrun us," Newsom said. "The reality is we're living in an era of extremes: extreme heat, extreme drought — and with the flooding we're experiencing around the globe."

Click to find a state sponsored cooling center 

Newsom's declaration followed a "Flex Alert" call for conservation for Thursday afternoon by the California Independent System Operator, which oversees the state's electrical grid.

In August 2020, a record heat wave caused a surge in power use for air conditioning that overtaxed the grid. That caused two consecutive nights of rolling blackouts, affecting hundreds of thousands of residential and business customers.

Rolling blackouts "are a possibility but not an inevitability" during the current heat wave, said Elliot Mainzer, president and CEO of California Independent System Operator.

Cooling centers were being opened across the state and officials encouraged people to seek comfort at public libraries and stores — even if just for a few hours to prevent overheating.

The heat wave and low humidity levels will also lead to worsening wildfire conditions in hills, forests and fields already bone-dry from months of drought.  

"After several days of strong heat, conditions will be much drier which may introduce some level of fire weather risk," the weather service said. "Drier fuels make for easier fire starts related to human activity."

The weather service said the only condition lacking this weekend for a Red Flag Warning was the absence of gusty winds, but a major fire still erupted in Southern CaIifornia. The Route Fire in Castaic in northwestern Los Angeles County raged through about 4,625 acres of hills containing scattered houses. Interstate 5, a major north-south route, was closed by a blaze that burned several hundred acres in only a few hours.

Media reports showed a wall of flames advancing uphill and smoke billowing thousands of feet into the air while planes dumped water from nearby Castaic Lake. There were no immediate reports of damage to buildings but a mobile home park with 94 residences was evacuated.

Eight firefighters were treated for heat-related problems, including six who were sent to hospitals, but all were in good condition, Los Angeles County Fire Department Deputy Chief Thomas Ewald said.

"Wearing heavy firefighting gear, carrying packs, dragging hose, swinging tools, the folks out there are just taking a beating," he said.

The elevated fire dangers forced officials to close a lot of Walnut Creek's open spaces including Lime Ridge, Shell Ridge, Sugarloaf, Borges Ranch, Howe Homestead Park and Acalanes Ridge. The closure of the parks will start today, and last through Labor Day Monday.  

First published on September 1, 2022 / 8:14 AM

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