This week's heat wave picked up momentum Thursday, scorching the Southland with triple-digit temperatures in many areas and prompting heat advisories and increased fire danger through the weekend.
National Weather Service forecasters said high pressure building over the area will be in full force by Friday and Saturday, bringing temperatures well above normal.
The system will result "in daytime high temperatures around 10 degrees above what is normally the hottest time of the year," according to the NWS.
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"Temperatures between 100 and 108 degrees will be common in the valleys and lower mountains of Los Angeles and Ventura counties ... with only modest relief at night."
Today's highs reached the 80s at the beaches, the 90s inland and above 100 degrees in the valleys.
An excessive heat watch will be in effect from Friday morning through Saturday night in the Los Angeles County Mountains, Santa Mountain Mountains Recreational Area and the Santa Clarita, San Fernando and San Gabriel valleys.
The Los Angeles County Department of Public Health issued a heat alert through Saturday for the Los Angeles Basin, the Pomona area and the San Fernando and Santa Clarita valleys. A separate heat alert is in effect today and Friday for the Antelope Valley and San Gabriel Valley.
With humidity expected to be low and gusty winds possible, a red flag warning indicating a heightened risk of wildfire will be in effect for some areas from 3 p.m. Friday through midnight Saturday night.
The red flag warning will be in effect in the Los Angeles County Mountains, Angeles National Forest and Antelope and Santa Clarita valleys.
Forecasters warned that triple-digit heat could present a danger to some residents, and demand for electricity could be high, creating the possibility of outages.
"Never, ever leave people or pets in enclosed vehicles, even for a short period of time," the NWS warned. "Take extra precautions if you work or spend time outside. When possible, reschedule strenuous activities to early
morning or evening. Know the signs and symptoms of heat exhaustion and heat stroke. Wear light weight and loose-fitting clothing when possible and drink plenty of water."
NWS officials noted, however, that there's not much chance of any heat records being broken.
"Friday through Sunday mark the 10-year anniversary of one of the hottest events on record for any month -- Woodland Hills hit 119 on July 22, 2006, the all-time high for any of our climate stations," according to the Weather Service.
Inland areas could see higher-than-normal temperatures as late as next Tuesday, although coastal areas should see some cooling beginning Sunday, forecasters said.