Saturday's high is expected around 101 degrees, pushing up to around 107 by Sunday.
Residents are encouraged to take precautions these coming days, especially by people who participate in outdoor activities, older adults, caretakers of infants and children and those sensitive to heat, county officials said in a news release.
The heat will be on "high" in the Desert Southwest the next several days.
Temperatures along the coast and in the western valleys will be somewhat cooler, but still 5 to 10 degrees above average, according to the weather service. PRECAUTIONARY/PREPAREDNESS ACTIONS.An Excessive Heat Warning means that a prolonged period of dangerously hot temperatures will occur. Locally higher temperatures are possible. Forecasters warn that overnight temperatures won't bring much relief.
The hot conditions are labeled as a classic pre-monsoon heat event for the Southwest region, NWS said.
Hirsh said temperatures are normally around 104 and 106 this time of year.
Symptoms of heat-related illness may include confusion, heavy sweating, weakness, headache, muscle cramps, rapid heartbeat, nausea or increased body temperature.
Temperatures are forecast to hit triple-digit territory in the San Fernando and Antelope valleys Friday and come close to doing the same in the Santa Clarita Valley on the fourth day of the Southland's heat wave, which air quality officials said is coinciding with exceedingly unhealthy smog levels.
Though the current NWS advisory ends on Sunday, ABC 7 says we might remain hot for a while, as "Looking forward into next week, this heat does not look to break.In fact, some of the hottest air in the United States will be centered over California".
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With one more birdie on the back nine, Matsuyama carded a sparkling seven-under 65, matching Fowler for the low round of the week. The leading South Africans are two-time US Open champion Ernie Els and Thomas Aiken, who are tied for 24th at 2-under-par.
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But they also know that Erin Hills could strike back if the wind kicks up and the course dries out a little or if the U.S. Scottie Scheffler, who just finished his junior year at Texas, had a 69 and amateur Cameron Champ had a 70 in his U.S.