This is what is keeping California cool while the rest of the U.S. sizzles
The Bay Area is already on track for one of its coolest starts to summer in decades, and forecast data suggest that trend isn't going anywhere. The Climate Prediction Center calls for continued below average temperatures across the state, essentially through the end of the month.
The lingering cool trend is a result of a broader atmospheric setup that's been locked in for weeks.
East of the Rocky Mountains, a sprawling and stubborn Bermuda high pressure system is pumping in heat, humidity and bouts of heavy rain. But over California, the jet stream has flattened into a fast-moving west-to-east flow of winds, interrupted only occasionally by subtle dips in the upper atmosphere. UCLA climate scientist Daniel Swain described this pattern as a ' sticky weak disturbance,' and the setup has been on repeat since early June.
The airflow around a stronger than normal North Pacific High continues to stir up cooler water along the West Coast, while driving a surge of warm water across the central Pacific. This sets up a positive feedback loop; cooler coastal waters sharpen the daily temperature and pressure gradients from the ocean to the Central Valley, which enhance onshore winds and reinforce the cloud deck. The result is more marine layer influence, lower high temperatures, especially near the coast.
It's not just the coast that's feeling the cooler temperatures. Inland areas that typically bake this time of year like the Central Valley, interior Bay Area and the high deserts, have struggled to mount any multiday heat waves. The kind of prolonged, widespread heat events California saw in July 2024 require a robust high pressure ridge centered closer to California, something that just hasn't materialized so far this summer.
The extended 8- to 14-day temperature outlook shows a similar pattern, with continued cool conditions across California. Still, the state won't avoid the heat altogether. Brief surges into the triple digits remain likely in places like Redding, Fresno and Palm Springs. But those hot spells will be short-lived and the marine influence will remain strong along the coast.
The cooler temperatures, both daytime and overnight, help tamp down fire weather risks. But as we push deeper into summer and fuels continue to dry, fire activity is still expected to increase.
Wednesday's weather in the Bay Area will be a continuation of the pattern, with daytime highs running about 10 degrees below normal and marking the coolest day of the week.
Wednesday outlook
San Francisco: A thick marine layer will generate patches of drizzle in the early morning. And from there, the clouds will be slower to retreat to the coast than yesterday. But retreat they will, leaving a mostly sunny Wednesday afternoon and evening. Temperatures will top out in the low 60s west of the Twin Peaks and in the mid-60s downtown and in the Mission. Winds from the southwest pick up during the afternoon and clouds will return after dark, with lows in the mid-50s.
North Bay: Pockets of drizzle will develop in Santa Rosa and along the Marin coast in the morning. Cloud cover from the marine layer will extend all the way back to Fairfield, but they will quickly break up by the early afternoon. Despite the sunshine, it's another cool day, with temperatures in the low to mid-70s. More clouds and drizzle overnight with lows in the 50s.
East Bay: A thick cloud deck will extend all the way to I-680 in the morning. Things will clear up rather quickly across the interior and south of Oakland, with clouds hanging on a bit longer in Berkeley and Richmond. Temperatures will range from the upper 60s to low 70s in the I-580/I-80 stretch, with highs in the mid-70s to around 80 degrees in Hayward, Concord and Livermore. Mostly cloudy again overnight with lows in the mid- to upper 50s.
Pacific Coast and Peninsula: Does the Pacific Coast see the sun this day? It's a tossup. Some sunshine may break through the clouds in the afternoon from Half Moon Bay up to Pacifica with temperatures in the low 60s. The rest of the Peninsula east of Skyline Boulevard will clear up earlier, with temperatures ranging from the upper 60s in South San Francisco, the low 70s in San Mateo and the mid-70s in Redwood City. The clouds return overnight with pockets of drizzle along the coast and lows in the 50s.
South Bay and Santa Cruz: A predominantly southwesterly wind will keep the clouds locked and temperatures muted for a good part of the day in Santa Cruz, where it will be a struggle to hit 70 degrees. The South Bay will once again be the warm spot in the region, with temperature in the low 80s. Mostly cloudy again overnight with lows in the mid-50s.
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