Southern California faces extreme heat and humidity, officials warn of health risks

Temperatures across much of Southern California topped 100°F on Wednesday, with humidity adding an extra 5 to 10 degrees to the perceived heat, according to the National Weather Service office in Oxnard. Meteorologist Bryan Lewis said the conditions meet extreme heat warning criteria, and the added moisture makes the "real feel" temperature especially uncomfortable.

The heat surge is driven by a strong upper-level ridge over Arizona and an offshore flow from the north and east, pushing temperatures 8 to 15 degrees above normal. Coastal areas saw highs in the mid- to upper-80s, while inland valleys reached 100-108°F. Dew points are projected in the 70s for most of Los Angeles and Ventura counties, a level that the agency describes as oppressive.

Public health officials have issued extreme heat warnings through Thursday and advise residents, particularly older adults, people with medical conditions, pregnant women, children and those without air conditioning, to limit outdoor activity, stay in cooled environments and check on vulnerable neighbors. Dr. David Eisenman of UCLA warned that high humidity hampers sweating, increasing the risk of dehydration, heart strain and overheating.

Experts noted that many Southern California homes lack air conditioning because the region historically enjoyed a milder Mediterranean climate. Climate change epidemiologist Tarik Benmarhnia said resilience to heat depends more on housing and lifestyle than any innate biological adaptation.

Forecasters expect a brief cooling of about five degrees on Thursday, with humidity remaining high. By Friday, temperatures are projected to fall another five degrees and humidity to decrease toward more typical levels, offering some relief after several days of oppressive conditions.