NWS attributes extreme heat to ridge of high pressure trapped over region
Downtown Los Angeles hit 104F (40C) on Monday, shattering the previous October 5 record of 101F (38.3C) set in 1953, according to the National Weather Service. About 30 miles south of Los Angeles, the city of Santa Ana recorded 106F (41.1C), up from the past daily high of 103F (39.4C) in 1953, the agency also reported.
The extreme heat reflects temperatures 15 to 20 degrees above normal for autumn across Southern California, with an unprecedented heatwave gripping the region. Extreme heat warnings were in place along the coast from Santa Barbara to San Diego through Thursday as health authorities advised the region’s millions of residents to limit outdoor activity and stay hydrated.
The NWS attributed the spell to a ridge of high pressure, in which hot air is trapped over a region. In San Diego and Los Angeles, the agency forecasted overnight temperatures hovering in the mid to upper 70s, a range the NWS noted provides only little relief from daytime highs.
The unusual spell has set records not only for its sweltering daytime temperatures but also for its prolonged length. Los Angeles recorded four consecutive days of 100F or more this past week, marking the longest streak of triple-digit temperatures in October for the city.
California’s coastal areas are expected to begin cooling starting Thursday, with rain in the forecast for the following week, according to the NWS. The state’s interior regions may also see cooler temperatures on Friday and Saturday.