Southern California has experienced some warm Octobers, but this fall started with an ongoing heat wave that broke records and ushered in an unusual number of 100-degree days.
The extreme heat is driven by a persistent ridge of high pressure that sits over the region, causing warm air to sink with little relief at night. At the same time, downslope winds and unusually warm ocean temperatures caused by El Niño reduced Southern California’s ocean breezes, which are often referred to as natural air conditioners.
For those who live in coastal areas, the unusually high temperatures may not even have much of an impact.
“We’re entering our fourth day of a really severe heat wave, and we still have a few days of high temperatures,” said Ross Schoenfeld, a meteorologist with the National Weather Service in Oxnard. “We do have heat events in October, but 100-plus days in a row is definitely starting to become quite noticeable.”
The average number of 100-degree days in downtown Los Angeles in October has been closer to 0 than 1 since the weather service started keeping records. So far this month, temperatures in the city center have reached 100 degrees or higher three days in a row, and could reach a fourth, according to the weather service.
If temperatures reach 100 degrees on Monday, “it will be the longest number of 100 or higher days we’ve ever seen in October at this location,” Schoenfeld said. The Weather Service maintains records of downtown Los Angeles from the 1800s.
The current heatwave has broken daily heat records across the South.
The temperature at Burbank Airport reached 101 degrees on Sunday, breaking the previous record of 100 degrees set in 1964. The temperature at Camarillo Airport reached 99 degrees, just above the previous record of 98 degrees set in 1953. The temperature in Oxnard reached 99 degrees on Sunday, breaking the previous single-day record of 94 degrees set in 2023.
In Orange County, Anaheim hit 101 degrees on Sunday, breaking the previous record of 98 degrees set in 2020.
The temperature in San Diego reached 100 degrees, breaking the previous record of 97 degrees set in 1987. The temperature at Oceanside Harbor reached 98 degrees on Sunday, breaking the previous record of 97 degrees set in 1953. Ramona reached 101 degrees, just surpassing the previous record of 100 degrees set in 1987.
Temperatures are expected to remain 15 to 22 degrees above normal on Thursday. Highs along the coast and valleys will be in the upper 90s to upper 100s over the next few days. Even the beach can’t provide relief from temperatures in the 80s.
The ocean is also at risk as Hurricane Rachel, hundreds of miles off the coast of Baja California, is expected to cause early and late tides and elevated surf starting Tuesday.
The weather service warned of dangerous rip currents and 3- to 6-foot waves at beaches in Catalina Island, Santa Barbara Islands, Los Angeles and Ventura counties. The most vulnerable areas are Long Beach and Port Avalon on Tuesday and Wednesday, and Malibu to Ventura County on Wednesday through Friday.
According to the Bureau of Meteorology, “Some vulnerable low-lying coastal areas may experience moderate sea flooding, particularly during morning and evening high tides, including beach car parks, cycle paths and harbor walkways. Moderate beach erosion is possible.”
Those seeking relief won’t find answers overnight.
Forecasters say the weather will remain warm after dark, with temperatures only dipping into the 60s and 70s in much of the region. Weather services in Oxnard and San Diego have issued extreme heat warnings until 8 p.m. Thursday, warning people of the risk of heat-related illness.
“We’re about to enter day four of this really severe heat wave, and we still have several days of high temperatures,” Schoenfeld said, noting that the lack of overnight recovery and consecutive days of hot weather “can cause real stress on the body over time, especially for older adults and other vulnerable populations, such as young children.”
The hot weather is expected to ease over the weekend, with temperatures reaching the mid-80s, and there could even be a chance of light showers on Sunday as Hurricane Rachel continues to move across the Pacific.