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As wildfires burn across California, areas of Ventura and Los Angeles Counties were under a red flag warning Sunday night due to extremely hot, dry conditions heightening the risks of fires.

A record-breaking heat wave gripped the Southern California region over the weekend, bringing even hotter triple-digit temperatures Sunday. Los Angeles County saw its highest temperature ever recorded — a sweltering 121° in Woodland Hills, according to the National Weather Service. That’s hotter than any temperature officially recorded in Ventura, Santa Barbara and San Luis Obispo counties, the agency said. A temperature of 117° was recorded in Woodland Hills on Saturday.

The day before Labor Day was “one of the hottest days since weather records began across much of southwestern California,” the National Weather Service said in a report released Sunday evening.

“After a very hot day yesterday, last night was exceptionally warm to hot across the region,” the report reads, noting that overnight temperatures in some areas of SoCal stayed above 100 degrees.

Temperatures soared into the afternoon, reaching record highs in Van Nuys and Burbank, where a temperature of 114 degrees tied with the area’s previous all-time high, according to forecasters. The cities of Lancaster, Palmdale and Camarillo also saw triple-digit temperatures that were the highest officially recorded in those areas, the National Weather Service said.

Low humidity amid the scorching heat was expected in the mountains of Los Angeles and Ventura counties as a red flag warning took effect at 6 p.m. Sunday, forecasters said. Gusty, northerly winds are expected to accompany the extremely hot conditions. Forecasters also warned of dry, hot weather bringing fire risks to counties further south in Southern California.

“We’re witnessing weather conditions that can quickly generate dangerous and fast-moving wildfires, especially in communities that are near foothills, canyons and wildland areas,” Kevin McGowan, director of the Los Angeles County Office of Emergency Management, said in a statement.

Around the same time the red flag warning took effect, California’s Independent System Operator declared a Stage 2 Emergency, warning that rotating power outages on Sunday are “likely.”

The operator of much of the state’s electrical grid called on Californias to reduce their energy usage to prevent blackouts. Meanwhile, a statewide Flex Alert also telling residents to conserve power remained in effect through 9 p.m.

Amid the extreme heat, more than 80,000 utility customers lost power in Los Angeles County in blackouts extending to several other parts of SoCal through early Sunday evening, officials said.

Valley and desert areas of southwestern California saw temperatures between 110 and 120 degrees on Sunday while temperatures soared past 100 degrees in parts of the region’s coastal plain, where they rarely exceed the triple digits.

In Riverside County, a temperature of 104 degrees in the community of Idyllwild broke a record for the all-time highest temperature in the area, forecasters said. Further south, in San Diego County, another all-time highest temperature of 115 degrees was recorded in Escondido.

The National Weather Service issued a Fire Weather Watch for Yucaipa and other valley areas in San Bernardino and Riverside counties. The alert warning of increased fire risks due to dry, hot weather is expected to stay in effect from Tuesday afternoon through Wednesday evening.

It also applies to the Inland Empire and mountain areas of San Bernardino and Riverside counties, forecasters said.

Dangerous heat in areas ravaged by wildfires complicated firefighting efforts as at least a dozen exceeding 1,000 acres burned across the state. An excessive heat warning was expected to stay in effect through Monday night in Yucaipa, where firefighters battled the flames of the El Dorado Fire in scorching temperatures. Around 8 p.m., as firefighting efforts continued, it was about 91 degrees.

The El Dorado Fire doubled in size to more than 7,000 acres by Sunday evening while remaining at just 5% containment. Earlier, fire officials said the weather could present a considerable challenge.

“Today’s weather is a concern as it’s predicted to be the hottest day of the heatwave,” officials with the San Bernardino National Forest said Sunday morning. “The vegetation is also extremely dry.”