Forget hot beverages and fall sweaters, this autumn in Southern California has been marked by what feels like a continuation of summer.
The extreme heat is driven by a persistent high-pressure ridge that has parked over the region, causing sinking warming air with very little overnight relief. That is paired with down-sloping winds and uncharacteristically warm ocean temperatures — driven in part by an El Niño that has reduced Southern California’s sea breeze, frequently known as its natural air conditioning.
The Southland has experienced hot Octobers in the past, but if this feels different, it’s because it is, according to climate experts.
The hot weather, which has kept people indoors and forced those without air conditioning to seek refuge at cooling centers, is expected to last through much of the week.
“This is not going to be a heat wave that suddenly breaks in a dramatic fashion,” said UC Agriculture and Natural Resources climate scientist Daniel Swain. “It’s likely going to remain significantly warmer than average for some time to come. This will probably end up being, at least in some parts of Southern California, one of the warmest Octobers on record, and perhaps across a broader portion of California and the West too.”
Here’s what we know:
How hot will it get?
Temperatures between 15 and 22 degrees above normal are expected to persist through Thursday. Highs along the coasts and valleys will be in the 90s and up to the low 100s in the coming days. Even the beaches will provide little relief, with temperatures in the upper 80s.
And those looking for relief won’t find it overnight.
It’ll still be warm after dark too, forecasters say, with the mercury dipping only into the upper 60s to mid-70s across much of the region. The weather service in Oxnard and San Diego issued extreme heat warnings through 8 p.m. Thursday, cautioning of the risk of heat-related illnesses.
A lack of overnight recovery and days of hot weather can “really build and stress the body over time, especially for the elderly and other vulnerable folks like the very young,” said Rose Schoenfeld, a meteorologist with the National Weather Service in Oxnard.
The Los Angeles Department of Public Health is urging residents to hydrate, avoid going outside during the hottest hours of the day, use an umbrella and wear lightweight clothing if you must go out — and take frequent breaks in air conditioned spaces. The county has dozens of cooling centers open.
Heat has shattered records
The heat wave has shattered multiple records including in downtown Los Angeles, which is on a four-day consecutive streak of temperatures of 100 degrees or higher — the longest consecutive stretch in October since records began.
Downtown Los Angeles broke a daily heat record Monday with the mercury reaching 104, shattering the previous record of 101 set in 1954 and tied in 1971.
Downtown currently is tied for the most 100-degree-plus days in October with those in 1958 and 1971, but could surpass those years if the mercury hits 100 degrees Tuesday, according to Schoenfeld.
The average number of 100-degree days in downtown Los Angeles in a typical October has been closer to zero than one since the weather service began keeping records in the late 1800s, according to the weather service.
Other heat records fell over the weekend.
Burbank Airport hit 101 on Sunday, breaking the previous record of 100 set in 1964. Camarillo hit 99, inching past the previous record of 98 set in 1953. And Oxnard hit 99 on Sunday, shattering the daily record of 94 set in 2023.
In Orange County, Anaheim hit 101 degrees Sunday, blowing past the 98-degree record set in 2020.
San Diego hit 100 degrees, toppling a record of 97 set in 1987. The Oceanside Harbor registered 98 on Sunday, toppling the record of 97 set in 1953. And Ramona hit 101, just past the record of 100 set in 1987.
Is it usually this hot in October?
It can be hot in October, but it’s generally not this sweltering for this long, according to Swain.
California often sees higher temperatures in September and October along the coast than in June and even July because of the marine layer that keeps things cool during those months. The marine layer typically recedes this time of year, resulting in higher temperatures, particularly along the coast, he said.
“But even by that standard, this has been extraordinary,” he said. “Not just because it’s been very hot day and night on individual days, but because there has been multiple consecutive days where we’ve reached these extreme temperatures, and it just is continuing on and only slowly fading.”
“So, is this completely unprecedented? No. Is this typical for October? Definitely not,” he added.
When will the scorching temperatures end?
The heat is expected to relent a bit by the weekend with temperatures in the mid-80s and even a chance of light showers Sunday as Hurricane Rachel continues its path across the Pacific Ocean.
But Swain said models suggest that temperatures won’t decline that much as October continues.
“This is not a cool autumn by any means,” he said.
