LOS ANGELES - A red flag warning signifying a high risk of wildfire will be in effect in parts of Los Angeles and Orange counties Friday amid Santa Ana winds, single-digit humidity and high temperatures on the final day of the region's latest heat wave.
Surface high pressure that has built into the Great Basin is helping to strengthen the offshore flow over L.A. and Ventura counties, generating a moderate Santa Ana wind event over the San Gabriel Mountains in both counties, producing winds of 35 to 45 miles per hour, said the National Weather Service.
"This combined with humidities lowering into the single digits will create several hours of critical fire weather conditions to this area," according to an NWS statement.
The red flag warning will be in effect from 3 a.m. TO 6 p.m. Friday in the San Gabriel Mountains in L.A. and Ventura counties, the Angeles National Forest, Ventura County's Los Padres National Forest, the Santa Clarita Valley, Orange County's Santa Ana Mountains and inland Orange County cities.
Northeast winds of 20 to 30 miles per hour with gusts of up to 45 mph will blow in the San Gabriels in and around the Antelope Valley (14) Freeway corridor amid humidity levels as low as 6 percent. The warning replaces the somewhat less serious fire weather watch that was in effect Thursday.
A heat advisory, meanwhile, will be in effect until 5 p.m. along the Los Angeles County coast, in Malibu, Santa Monica and other beach cities, in downtown Los Angeles, Hollywood, Beverly Hills, the San Gabriel and Santa Monica mountains, the San Fernando, Santa Clarita and San Gabriel valleys, and inland Orange County, indicating temperatures could threaten human health.
"Hot temperatures may cause heat illnesses to occur," warned a weather service statement. ``Those without air conditioning will be especially vulnerable during this extended heat wave. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors."
The weather service stressed that children, seniors and pets should never be left unattended in vehicles under any circumstances, even with windows open as car interiors can quickly turn lethally hot.
The hot weather prompted the California Independent System Operator, which manages the state's power grid, to issue a Flex Alert that was in effect until 10 p.m. Thursday. The alert urges residents to voluntarily cut their power to prevent strain on the grid, which could potentially lead to rolling power outages.
Residents were urged to take steps to cut power, such as delaying the use of major appliances, turning off unnecessary lights and closing curtains and drapes to cool homes.
The NWS said a record high for an October 15 was set Thursday in Woodland Hills, where the high was 105, and the record high 86 in Sandberg tied the record set in 1991.