Southland residents were getting one last day of relatively mild weather Wednesday before temperatures begin climbing Thursday, with dangerous heat expected to peak over the weekend.
“Seasonably warm temperatures today will shift to dangerously hot by Friday through the weekend as the next heat wave arrives,” according to the National Weather Service.
Wednesday’s temperatures are expected to remain only a few degrees above average before a strengthening high-pressure system expands westward, forecasters said.
Widespread moderate to high heat risk is expected Friday through the weekend, when temperatures are forecast to climb into the mid-90s to 105 degrees across most inland communities.
“The extreme pressure being exerted from aloft will force temperatures at the surface to rise to around 10 degrees above normal in many areas, resulting in significant heat stress, especially in areas that have limited or no access to cooling sources,” forecasters said.
The weather service issued an extreme heat warning that will be in effect from 10 a.m. Thursday through 8 p.m. Sunday for the Antelope Valley and Antelope Valley Foothills, where temperatures of 104 to 114 degrees are possible.
In the western San Gabriel Mountains and the 5 and 14 Freeway corridors, a heat advisory will take effect at 10 a.m. Thursday, with triple-digit temperatures anticipated, but it will be replaced by a more severe extreme heat warning at 10 a.m. Friday through 8 p.m. Sunday, when highs are expected to range between 95 and 105 degrees.
An extreme heat warning will also be in effect from 10 a.m. Friday through 8 p.m. Sunday for the Santa Monica Mountains Recreational Area, Calabasas, Agoura Hills, the San Fernando and San Gabriel valleys and the Los Angeles inland coastal area, including downtown. Those areas could see “dangerously hot conditions” with temperatures of 95 to 110 degrees, according to the NWS.
The eastern San Gabriel Mountains will be under a heat advisory starting at 10 a.m. Thursday and continuing through 8 p.m. Sunday, while Los Angeles County beaches, the Malibu coast and Palos Verdes Hills will be under a heat advisory from 10 a.m. Friday through 8 p.m. Sunday. All of those areas could see temperatures as high as 100 degrees, forecasters said.
“Current forecast highs are near or exceeding record temperatures in many areas, especially Friday and Saturday,” the NWS said.
In Orange County, temperatures are expected to remain only a few degrees above average Wednesday before warming begins Thursday. Forecasters said the hottest conditions are expected Saturday, with Anaheim forecast to reach 92 degrees Friday and 95 Saturday.
An extreme heat warning will be in effect from 10 a.m. Friday through 8 p.m. Sunday in the Santa Ana Mountains and foothills, with temperatures up to 103 possible, and in Orange County inland areas, which could have temperatures in the upper 90s. A less severe heat advisory will impact Orange County coastal areas from 10 a.m. Friday through 8 p.m. Sunday, with highs expected in the mid-80s to lower 90s.
“One positive aspect is that humidities have been decreasing as tropical moisture remains east and south of the area. This is allowing overnight temperatures … to cool a few degrees, providing some relief,” the NWS said. “However, models are strongly suggesting increasing moisture aloft later this week and weekend during the peak of the heat wave, which will further exacerbate the heat stress over the area.”
The weather service also warned that hot, unstable conditions and pockets of gusty winds could elevate the risk of large wildfires heading into the weekend.
“High temperatures will begin to cool a few degrees for Sunday and Monday, but still be around 10 degrees above average for inland areas on Monday with extreme Heat Risk for the deserts,” the NWS said.
The Los Angeles County Department of Public Health urged residents to take precautions, warning that prolonged high temperatures and warm overnight conditions increase the risk of heat-related illness.
“Heat causes more deaths in the U.S. annually than floods, storms and lightning combined,” Los Angeles County Health Officer Dr. Muntu Davis said. “If you or someone around you experiences symptoms of heat stroke or heat exhaustion, such as dizziness, nausea, rapid heartbeat, confusion or passing out, seek medical help immediately.”
Public health officials urged residents to stay hydrated, limit outdoor activity during the hottest part of the day, seek air-conditioned spaces if their homes become too warm and check on older adults, children and others at greater risk of heat-related illness. Officials also reminded residents never to leave children or pets unattended in vehicles, even for a short time.