Southern California enters week-long heatwave with temperatures near 100F

Friday’s Los Angeles temperature nearly 7F above the prior October 2 record

The National Weather Service issued long-duration heatwave advisories for Southern California on Friday, with temperatures expected to hover near 100F in downtown Los Angeles and to run well into the triple digits farther inland through at least the coming week.

“We’re expecting temperatures will run some 15-20 degrees above normal – that’s pretty significant,” said Richard Bann, a meteorologist with the NWS’s Weather Prediction Center. “Stay cool. Stay hydrated. Limit exposure to the sun.”

Friday’s heat already reached an exceptional level. “The extremely hot temperature Friday is rare,” said V Kelly Turner, a professor of geography and urban planning at UCLA. “Nearly 7F hotter than the hottest October 2 ever and about 30 degrees higher than historical averages around 75F.”

The unseasonable warmth stems from ridges of high pressure that park themselves above the region during October, a pattern that is not uncommon in Southern California. This year’s heat is also influenced by an ongoing marine heatwave that is, in turn, driving a strong El Niño, the climate pattern of above-average Pacific Ocean surface-water temperatures.

“It’s difficult for scientists to point to a specific event and describe it as an effect of climate change,” said David Neelin, an atmospheric physicist who researches climate change at UCLA. Research shows that with every half-degree of global warming, heatwaves become both more likely and longer lasting.

“Overall, it’s hard to escape that a warmer climate adds to the strength of heatwaves,” Neelin said. “It adds to the probability of heatwaves and the likelihood of getting longer-duration heatwaves.”

The increased heat and low soil moisture leave the region more vulnerable to wildfires, though current forecasts do not call for the strong winds that typically spread fast-moving blazes.

Edith de Guzman, a UCLA researcher who studies climate change and heat adaptation, said longer-duration heatwaves are becoming more common. “Climate change is making longer-duration heatwaves possible, while simultaneously increasing their frequency and intensity,” she wrote. “So we should prepare for more of this in the future.” De Guzman urged governments to invest in heat adaptation now to make the region more livable in the future, and called providing more shade “the most effective way to keep people safe” in a text message.

The heat will coincide with major outdoor events in the region, including Game 1 of the National League Division Series between the Los Angeles Dodgers and the Atlanta Braves on Saturday.