Southern California has had some toasty Octobers, but the start of this year’s fall season was marked by a lingering heat wave that broke records and ushered in an unprecedented run of 100-degree daily temperatures.
The extreme heat is being driven by a persistent ridge of high pressure that has parked itself over the region, causing warm air to drop with very little relief overnight. Added to this are downslope winds and unusually warm ocean temperatures – caused in part by an El Niño phenomenon that reduced Southern California’s sea breeze, often known as natural air conditioning.
“We are on day four of this very significant heat wave and we have several more days of heat,” said Rose Schoenfeld, a meteorologist with the National Weather Service in Oxnard. “We have heat spells in October, but that 100-plus day streak is definitely starting to become pretty notable.”
The average number of 100-degree temperature days in downtown Los Angeles during a typical October has been closer to zero than one since weather services began keeping records in the late 1800s. This month, downtown Los Angeles is experiencing a streak of four consecutive days of temperatures of 100 degrees or higher — the longest consecutive streak in October since records began.
Downtown is currently tied for the most days with temperatures above 100 degrees in October with 1958 and 1971, but could surpass those years if the mercury hits 100 degrees on Tuesday, according to the weather service.
“If we get another one tomorrow, then we would be at most over 100 degrees in October in downtown Los Angeles,” Schoenfeld said.
The current heatwave has already broken daily heat records across the Southland.
Downtown Los Angeles broke a daily heat record on Monday, with the mercury reaching 104 degrees, breaking the previous record of 101 set in 1954 and matched in 1971.
Burbank Airport reached 101 degrees on Sunday, breaking the previous record of 100 set in 1964. Camarillo reached 99 degrees, slightly surpassing the previous record of 98 set in 1953. And Oxnard reached 99 degrees on Sunday, breaking the daily record of 94 set in 2023.
In Orange County, Anaheim reached 101 degrees on Sunday, surpassing the record of 98 degrees set in 2020.
San Diego reached 100 degrees, toppling a record of 97 set in 1987. Oceanside Harbor recorded 98 on Sunday, toppling the record of 97 set in 1953. And Ramona reached 101, just shy of the record of 100 set in 1987.
“It’s going to be pretty darn hot,” Daniel Swain, a climatologist at UC Agriculture and Natural Resources, said of this week during a recent briefing on his Weather West channel.
Temperatures between 15 and 22 degrees above normal are expected to persist through Thursday. Highs along coasts and valleys will be in the 90s to 100s over the next few days. Even the beaches will provide little relief, with temperatures hovering in the 80s.
The ocean is expected to bring its own dangers starting Tuesday with high morning and evening tides and high waves in the wake of Hurricane Rachel, located several hundred miles off the coast of Baja California with sustained winds of up to 85 mph.
The weather service is warning of dangerous rip currents and high waves of 3 to 6 feet on Catalina and Santa Barbara Islands as well as beaches in Los Angeles and Ventura County. The most sensitive areas will be Long Beach and Avalon Harbor Tuesday and Wednesday, then Malibu through Ventura County Wednesday through Friday.
“Moderate seawater flooding is a possibility in some vulnerable low-lying coastal areas, particularly around morning and evening high tides, including at beach parking lots, bike paths and harbor walkways. Moderate beach erosion is possible, if not likely,” according to the weather service.
And those looking for relief won’t find it overnight.
It will still be warm after dark, forecasters say, with the mercury only dipping into the 60s to mid-70s across much of the region. Weather departments in Oxnard and San Diego issued extreme heat warnings until 8 p.m. Thursday, warning of the risk of heat-related illnesses.
Schoenfeld said a lack of nighttime recovery and hot weather days can “really strain and stress the body over time, especially for older adults and other vulnerable people like the very young.”
The Los Angeles Department of Public Health urges residents to stay hydrated, avoid going outside during the hottest hours of the day, use an umbrella and wear light clothing if you must go out – and take frequent breaks in air-conditioned spaces. The county has dozens of cooling centers open.
The heat is expected to ease a bit by the weekend with temperatures hovering around the 80s and even a chance of light showers on Sunday as Hurricane Rachel continues its path through the Pacific Ocean.
But Swain, the climatologist, said models suggest temperatures won’t drop as much as October continues.
“It’s not a cool fall by any means,” he said.
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