Coastal California, stretching from the Bay Area to parts of Southern California, has recorded its coolest June 1 to August 1 period since at least 1979, defying typical summer expectations. Millions of residents have experienced unseasonably low temperatures, a stark contrast to the usual warm and sunny conditions. This unusual weather pattern has been attributed to a persistent low-pressure system and a strong marine layer along the coast.
The pronounced chill has impacted various locations across the region, with specific areas reporting record-breaking cool temperatures. According to a recent tweet by Mike Netter, "Petaluma, in the North Bay, has had weather more typical of Fairbanks, Alaska, this summer." This highlights the significant deviation from normal summer conditions in the area.
San Francisco, known for its mild summers, has seen only two days above 70°F since June 1, making its average afternoon high downtown 63.7 degrees, which is 2.7 degrees below normal and the coldest since 1999. Further south, Monterey's highest temperature this summer has reached only 71°F, a notable departure as "Every other summer on record since World War II has had at least one day reach 74°F or higher," Netter stated.
The cool trend extends to the Central Coast, with Lompoc experiencing its coldest summer to date since 1971. In Southern California, Santa Monica's highest temperature for the entire summer has been 77°F. This persistent coolness along the coast stands in sharp contrast to inland California, where many areas have been experiencing triple-digit heatwaves.
Meteorologists explain that a persistent low-pressure system over the Pacific Northwest and California, coupled with enhanced coastal upwelling and a strong marine layer, has acted as a natural air conditioner for the coastal regions. While forecasts initially suggested above-normal temperatures for parts of California, the observed reality has been a prolonged period of unseasonable coolness. Experts suggest that this pattern could persist into early August, though a warm-up is anticipated later in August or September.