A heat wave will start rolling over the Southland today, sending temperatures into triple-digit territory in some L.A. County valley communities and posing a threat to human health.
A heat advisory issued by the National Weather Service will be in effect from late Saturday morning through early Sunday evening in the San Fernando, San Gabriel and Santa Clarita valleys and both the San Gabriel and Santa Monica mountains.
The NWS forecast a mix of sunny and partly cloudy skies in L.A. County today and highs of 77 degrees at LAX; 81 in Avalon; 84 on Mt. Wilson and in Long Beach; 85 in Downtown L.A.; 91 in San Gabriel; 92 in Burbank; 93 in Pasadena; 95 in Saugus; 98 in Woodland Hills; 102 in Palmdale; and 103 in Lancaster.
Weather.com is predicting high temperatures for L.A.'s Eastside today in the high-mid-80s.
The National Weather Service attributed the hot weather to a strong upper level high centered over Arizona and New Mexico. It will expand westward through Sunday before weakening somewhat on Monday.
The weather service urged area residents to stay hydrated by drinking plenty of water, confining strenuous work or exercise to early morning or evening hours, and wearing light-weight clothing.
And, it stressed, "never, ever, leave children, elderly and pets in and enclosed car, even with the windows down during this heat."
The NWS forecast temperatures of 100-110 in the Antelope Valley, 95-105 in L.A. County's other valleys and 92-102 in the mountains and foothills.
Sunday will be the heat wave's warmest day, with highs of 101 forecast in Woodland Hills and 106 in Palmdale and Lancaster. Temperatures in the 90s in some valley areas will last at least through Thursday.
Sunny skies were forecast in Orange County, along with highs of 74 in San Clemente; 76 in Newport Beach and Laguna Beach; 83 on Santiago Peak; 87 at Fremont Canyon and on Ortega Highway at 2,600 feet; 88 in Irvine; 89 in Mission Viejo; 90 in Yorba Linda and Fullerton; and 91 at Trabuco Canyon and in Anaheim. A cooling trend is expected Monday.