As autumn arrives, temperatures climb, not fall, in Southern California

Potentially record-breaking heat, warm ocean waters and muggy nights. These are typically the tell-tale signs of summer.

But with another sweltering weekend expected across Southern California, it turns out Wednesday marks the beginning of fall in name only.

“It’s definitely going to feel like summertime� this weekend, said Stuart Seto of the National Weather Service in Oxnard. “Hot, hot, hot.�

From the coast to downtown L.A., the valleys to the high desert, a high-pressure system settling over Los Angeles County on Thursday is expected to keep temperatures 10 to 12 degrees warmer than average, Seto said.

The hottest day will be Saturday, when temperatures could climb to 94 downtown and 100 in Lancaster, Seto said.

The hot days are fueled by unusually warm ocean waters, which limits the cooling effect from ocean breezes at night. The warm-water phenomena has been dubbed “the blob� by experts, and its origin is unknown. The blob stretches from Southern California to Alaska and has affected marine life and the commercial fishing industry along the way.

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“It’s been sitting out there. … It’s really significant because we’re not getting the overnight cooling. By the time we get to daytime, we’re starting out warmer, so it’s going to get warmer,� Seto said.

After sunset, temperatures will still hover in the upper 60s, which is up to 7 degrees warmer than normal for this time of year, Seto said.

For breaking California news, follow @JosephSerna.

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