The searing heat that has baked the Southland in recent days is expected to continue through the Labor Day weekend, with excessive-heat warnings in place into next week.
Record-setting temperatures have already been recorded in some areas and state officials are calling on the public to limit use of electricity to minimize strain on the power grid.
"We are anticipating this extreme heat to be a length and duration the likes of which we haven't experienced in some time,'' Gov. Gavin Newsom said Wednesday. “Yes, we're used to record-breaking temperatures, maybe a day or two, more episodic, but this is an extended period.''
The California Independent System Operator, which manages the power grid, has called for multiple evening Flex Alerts, including 4 to 9 p.m. Saturday, urging the public to limit their use of power over during that period.
"With excessive heat in the forecast across much of the state and Western U.S., the grid operator is expecting high electricity demand, primarily from air conditioning use, and is calling for voluntary conservation steps to help balance supply and demand,'' according to Cal-ISO.
Extreme heat and low humidity also create elevated fire weather conditions, the National Weather Service cautioned. On Wednesday, the Barrett Fire, a major brush wildfire, broke out in the far southern reaches of the San Diego area, now having blackened more than 4,400 acres, leveling three houses, injuring six people, and forcing widespread evacuations and road closures.
An excessive-heat warning is in effect for parts of San Diego County until 8 p.m. Tuesday. Dangerously hot conditions with temperatures up to 100 degrees are in the forecast for San Diego coastal areas. Extreme heat is expected in Oceanside, Vista, Carlsbad, Encinitas, Chula Vista, National City and San Diego.
San Diego valleys and mountains will experience extreme heat as well. Temperatures in the valleys are expected to be between 97 and 105 degrees and in the mountains between 91 and 101 degrees.
The excessive-heat warning also is in effect in Escondido, El Cajon, San Marcos, La Mesa, Santee, Poway, Julian and Pine Valley.
The heat wave began Monday, then intensified Tuesday and Wednesday.
Campo reported a record high of 105 for Aug. 31, tying the mark set in 1998.
"Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors,'' the NWS advised. "Young children and pets should never be left unattended in vehicles under any circumstances.''
Forecasters also urged residents to be aware of the signs of heat stroke.
"Take extra precautions if you work or spend time outside,'' the NWS cautioned. “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. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments.Anyone overcome by heat should be moved to a cool and shaded location.''
Temperatures will be more manageable at the beaches during the extra-hot spell, but will still climb into the upper 80s. Overnight lows will not offer much relief, staying in the 70s and even in the low 80s in some of the hotter areas.
Meanwhile, with Flex Alerts expected to continue into next week, particularly on Sunday and Monday — which are forecast to have the highest electricity demand — residents are urged to take power-saving steps including:
— setting thermostats to 78 degrees or higher;
— avoiding use of major appliances;
— turning off unnecessary lights; and
— avoid charging electric vehicles.
Residents are also advised to pre-cool their homes as much as possible, and close blinds and drapes to keep interiors cool.