California is experiencing a severe end-of-summer heatwave, with record-breaking temperatures and unusually high humidity creating dangerous conditions, particularly in Southern California. The heatwave is expected to peak on Wednesday, with inland areas facing temperatures over 100 degrees Fahrenheit and coastal regions experiencing oppressive moisture.
"These are some of the highest humidities we’ve ever experienced in coastal Southern California," said UC climate scientist Daniel Swain. "There’s already some evidence that this summer has been, at least at some locations in Southern California, the most humid summer on record."
According to the National Weather Service (NWS), maximum temperatures reached the mid- to upper 80s at the beaches, the 90s along the coast, and between 100 and 108 degrees in inland valleys. Meteorologist Henry DiCarlo noted that dew points in many areas reached 76%, a level comparable to a tropical forest and higher than typically observed in Florida.
The NWS defines a dew point of 55 or below as "dry and comfortable," while a dew point of 65 or above is considered "oppressive." An extreme heat warning has been issued across the region, including areas like the Malibu Coast, Los Angeles County Beaches, Catalina, and the San Gabriel Valley, remaining in effect through Thursday.
This extreme weather phenomenon is attributed to the combination of lingering moisture from Hurricane Marie and a high-pressure ridge over the region. Hurricane Marie had previously impacted Southern California over Labor Day weekend, causing significant waves and flooding.
Northern California is also affected by the heat, with a heat advisory issued for the Bay Area. Temperatures in parts of the region approached 100 degrees, with San Jose forecasted to reach 96 degrees and Fairfield expected to hit 103 degrees.
Health officials are advising residents to stay hydrated, take frequent breaks, and seek out air-conditioned spaces to cope with the punishing conditions. 
