By admin 
October is here, but summer is hanging around for quite a bit longer.
Starting Friday and lasting through at least the next week, a heatwave will keep the western U.S. hot as we kick off the 10th month of the year. The result will be a prolonged stretch of above average temperatures for nearly all of California, with widespread highs in the 90s for the Central Valley and even portions of Southern California into the triple digits.
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On Friday, high temperatures will rise well into the 90s for the entire Central Valley, with 90s even creeping into the Bay Area and the Los Angeles metro. The air heats up further this weekend, with places like Merced and Fresno approaching 100 degrees Sunday as skies clear and high pressure pushes down from above.
These high temperatures are about 10–15 degrees above average across the board; Central Valley high temps for early October are normally in the mid-80s. The same change is true for low temperatures. The sun will rise on low temps solidly in the 60s through the Central Valley, Bay Area.
In Southern California, the rise in low temps is even more apparent — a Los Angeles low temperature in the mid-70s both Saturday and Sunday morning will quickly add heat stress for any households without air conditioning.
That is nothing to say of the back-to-back 100 degree high temperatures both days for the second-largest metro in the nation. Accordingly, an extreme heat warning has been issued for Southern California from Santa Barbara down through San Diego.
Heat alerts issued for much of Central and Southern California
Also issued for much of the southern two-thirds of the state is a heat advisory starting Saturday at 11 a.m. through Monday evening across most of the advisory area. From the Southern Sacramento Valley south to Bakersfield, the inland Bay Area, and the Central Coast, a large portion of Central California will be experiencing these hot temperatures all weekend long.
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The extreme heat warning for southern California is even more long-lasting, and is not set to expire until later Thursday. A weeklong heat alert is a sign that the confidence in this heat wave hanging around is high, and that any impacted plans should be adjusted accordingly. Not to a few days later, but potentially a few weeks later.
Heat wave will linger for at least another week
The reason for this is a massive ridge, or elongated area of high atmospheric pressure, building up across the western U.S. This dome of high pressure through the upper atmosphere centered over Southern California will clear the skies starting this weekend as air sinks from above, heating up the ground in the process. These setups can be stable and stubborn — ridges that are strong enough tend to dominate the rest of the weather pattern across North America and get stuck in place for a week or two at a time. That will be the case this go around.
The ridge will also snuff out the Delta breeze for Sacramento and the Delta region through at least the middle of next week. So unlike most of the summer, the heat will linger even longer into the evening and overnight hours.
The Climate Prediction Center, who forecasts these patterns out weeks and months at a time, said much of California and the west will experience these above average temperatures into the second week of October, meaning that the ridge that is settling in could stick around. Any substantial autumnal cool down seems like it would not arrive until mid- to late October at the earliest.
This story was originally published October 2, 2026 at 6:00 AM with the headline “Weekslong heatwave set for California. How long could it last?.”
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