The heat will be accompanied by gusty Santa Ana winds during a stretch when record-breaking temperatures between Friday and Sunday, National Weather Service forecasters said. A wind advisory will be in effect until 3 p.m. for a widespread part of Los Angeles.
The weather service forecast winds of 15 to 25 mph with gust up to 40 mph Gusts in mountain communities might reach 50 mph.
"Gusty winds will make driving difficult, especially for drivers of high-profile vehicles," warned an NWS statement. "When driving, use extra caution. Be prepared for sudden, gusty crosswinds."
Highs were forecast to be in the 80s Friday. Daytime highs Saturday and Sunday will range from the 80s to lower 90s at the coast and from the mid 80s to mid 90s in the valleys and foothills, forecasters said, blaming a ridge of high pressure.
The normal high for downtown Los Angeles is 70.
"It's not necessarily going to be cooler at the beaches," said NBC4 forecaster Crystal Egger. "When you have an off-shore Santa Ana wind, it bring the heat all the way to the coast."
NWS forecasters urged residents and visitors to avoid heat stress, including by scheduling outdoor activities in the morning or evening to avoid the day's strongest heat, wearing light clothing if engaging in strenuous activities, and staying hydrated.
The weather service issued an advisory for participants in Sunday's LA Marathon, saying they need to be aware of the potential for serious heat-related problems. The entire field will start at Dodger Stadium at 6:55 a.m., 30 minutes earlier than originally scheduled in an effort to beat the heat.
The race will have wave starts to ensure proper runner spacing and enable more efficient replenishment of supplies at aid stations. Additional water and Gatorade Endurance Formula will be provided at all 24 aid stations.
"Cooling buses" will be stationed along the course and at the finish line; misting stations, cold towels and ice will be provided
Sunday's high in metropolitan Los Angeles, an area that takes in the marathon course, is forecast to be 88.
The NWS forecast sunny skies today along with highs of 75 on Mount Wilson; 79 in Palmdale; 80 in Lancaster; 82 in Avalon and San Clemente; 85 in Saugus; 86 in Laguna Beach; 87 at LAX and Newport Beach; 90 in Mission Viejo, Pasadena, San Gabriel and Burbank; 91 in Woodland Hills; 92 in downtown L.A., Irvine and Yorba Linda; 93 in Long Beach and Anaheim; and 94 in Fullerton.