LOS ANGELES — Large sections of Southern California today remained under red flag warnings, signifying a high risk of wildfires because of powerful Santa Ana winds and low humidity levels.

The warnings were initially scheduled to expire Thursday night but were extended Tuesday and are now scheduled to be in force until Friday night.

The National Weather Service said the wind would weaken by 10 to 20 miles per hour today but would regain strength tonight. After that, gusts of 45 to 65 mph will be common.

“These winds will then gradually weaken Thursday night through the weekend,” according to the NWS. But humidity levels of only 6 to 15 percent will linger through at least early next week.

Isolated gusts up to 90 mph likely late Wednesday night through Thursday in remote canyon and foothill locations like the Cajon Pass in San Bernardino County, according to the NWS.

Both a high wind and red flag warning will remain in place for San Bernardino County until Friday, according to the NWS.

As of this morning, red flag warnings were scheduled to remain in effect until 8 p.m. Friday in the Santa Monica Mountain Recreational Area, the San Gabriel Mountains, the Angeles National Forest, the San Fernando, Santa Clarita and San Gabriel valleys, beach cities, metropolitan L.A., Downtown Los Angeles and the Hollywood Hills. No red flag warning was in force in the Antelope Valley.

A red flag warning was also in effect until 8 p.m. Friday in all of Orange County.

The wind in the red flag areas is expected to blow at between 15 and 35 mph with gusts of up to 50 mph in urban areas and up to 75 mph in the mountain, forecasters said.

The NWS forecast sunny skies in L.A. County today and highs of 60 on Mount Wilson; 63 in Palmdale and Lancaster; 69 in Saugus; 71 in Avalon; 75 in Woodland Hills; 76 in Pasadena, Northridge and Van Nuys; 77 in downtown L.A., North Hollywood, San Gabriel and at LAX; 78 in Torrance, San Pedro and West Covina; and 79 in Long Beach and Whittier.

Sunny skies were also forecast in Orange counties, along with highs of 71 in Laguna Beach; 72 in San Clemente; 74 in Newport Beach; 76 in Yorba Linda; 77 in Mission Viejo; and 78 in Fullerton, Anaheim and Irvine.

In San Bernardino County today, it will be 47 in Big Bear; 72 in San Bernardino; 74 in Redlands; and 75 in Ontario and Rancho Cucamonga.