Extreme heat warnings hold through Thursday from Los Angeles to the Inland Empire

Extreme heat warnings remained in force on Monday across coastal and valley Los Angeles and Ventura counties and across the San Bernardino and Riverside valleys, and they run until 8 p.m. PDT on Thursday 8 October. The National Weather Service office in Los Angeles and Oxnard said highs would reach 90 to 100 degrees at the coast and 106 in the valleys. The San Diego office, covering the Inland Empire, warned of upper 90s to 105 by day and overnight lows in the upper 60s to mid-70s.

The Los Angeles warning was issued as a continuation at 11:04 a.m. PDT on Sunday and lists Santa Clarita, Malibu, Torrance, Westlake Village, Avalon, El Monte, San Gabriel, Hollywood, Ojai, Beverly Hills, Thousand Oaks, Glendale, Fillmore, Long Beach, Burbank, Woodland Hills, Pomona, Simi Valley, Pasadena, Camarillo and Santa Monica among the named places. The Inland Empire warning was issued at 9:10 p.m. PDT on Sunday and updated on Monday morning. Both end at the same hour on Thursday. They are not the same product. One covers the coast and the Los Angeles basin. The other covers the inland valleys east of the basin. A resident in Pomona can fall under both descriptions depending on which zone line the forecast office draws.

Why the nights matter as much as the afternoons

The San Diego office's overnight range, upper 60s to mid-70s, is the part of the warning that changes the risk for people without cooling. A day at 100 degrees is dangerous in direct sun. A night that does not fall below 70 degrees removes the recovery that older houses and uncooled apartments usually get. The weather service language on both warnings is the same on the consequence: heat-related illness rises in events of this kind, and a closed car reaches lethal cabin temperatures in minutes. The listed actions are ordinary and specific: fluids, an air-conditioned room, staying out of the sun, and checking on relatives and neighbours. Children and pets are not to be left in vehicles.

ABC's Monday briefing said more than 35 million people were under alert for dangerous temperatures as the October heat covered California. That figure is a population under alert, not a count of people forecast to need medical care. The warnings themselves do not publish a casualty estimate. They publish temperatures, an end time, and a list of cities.

What Thursday changes

Both warnings expire at 8 p.m. Thursday. That is a forecast-office decision, not a promise that Friday is mild. If the ridge holds, the offices can extend the warnings. If onshore flow returns, they can let them lapse. The usable fact on Monday is the window already written: four more afternoons, through Thursday evening, with valley highs up to 106 and coastal highs still at or above 90.

October heat in Southern California is not rare. A warning that includes Avalon, on Santa Catalina Island, and Ojai, in an inland Ventura valley, in the same product is less ordinary. It means the marine layer is not doing the work it usually does on the coast. A 90-degree reading at the beach and a 106-degree reading inland, under the same end time, is the spread the Los Angeles office wrote into Sunday's continuation.

The practical distinction for the next four days is between places with reliable cooling and places without it. The warning does not sort cities that way. It sorts them by forecast high. Long Beach, Compton, East Los Angeles and Santa Monica are in the coastal and basin list. Santa Clarita, Fillmore and Ojai sit in the hotter valley language. The Inland Empire warning adds the San Bernardino and Riverside valley floors, with warm nights attached. Schools, outdoor work and evening sport all sit inside that window until Thursday at 8 p.m.