San Francisco just notched the kind of record that makes locals reach for another layer of Patagonia: the coldest Nov. 30 high in 103 years, courtesy of a stubborn Tule fog bank that turned the Bay Area into a refrigerated terrarium while much of California froze.
A century-old chill
On Sunday, downtown San Francisco managed a high of only 50 degrees, slipping past the previous Nov. 30 “cold high” mark of 51 set in 1922, back when the Golden Gate Bridge was still a gleam in an engineer’s eye. Meteorologists say a saturated lower atmosphere, primed by a wet October and November, helped trap moisture and cool air near the surface, locking in the chill.
Tule fog takes center stage
The star of the show is Tule fog, the dense Central Valley variety that usually keeps to farm fields and freeways but has spent days spilling into Bay Area counties under a persistent high-pressure ridge to the west and lower pressure to the east. Think of it as a 400-mile-long low cloud deck: great for moody sunrise photos, less great for anyone hoping the sun might actually show up before lunch.
From Spare the Air to spare the pipes
The same stagnant pattern that chilled San Francisco also forced the Bay Area Air District to issue a Spare the Air alert over Thanksgiving, as the fog and light winds bottled up surface pollution and briefly turned fireplaces into contraband. Farther south, the National Weather Service tacked on a freeze warning for parts of Southern California, including Death Valley, with temperatures expected to dip near 30 degrees and threaten crops and uninsulated plumbing—an unusual alignment of frost and desert branding.
Offshore winds and king tides on deck
Relief, such as it is, arrives via an “inside slider” system: a cold, dry low dropping through the Great Basin that will flip the pattern to gusty offshore winds of 30 to 45 miles per hour in higher Bay Area elevations, with stronger bursts on the tallest peaks. Those winds should scour out the boundary layer and thin the fog for several nights, even as localized pockets linger in spots like the Russian River Valley.
At the shoreline, the script tilts from gray to dramatic as 10- to 14-foot breakers and long-period swells pound the coast, raising the risk of sneaker waves while a beach hazards statement remains in effect. Layered on top: king tides arriving Tuesday through Sunday, expected to push water levels roughly a foot or more above normal and trigger minor coastal flooding in low-lying neighborhoods during morning highs—nature’s reminder that sea-level rise dress rehearsals don’t require rain.
A quiet, warmer epilogue—maybe
Beyond this week’s fog, frost and photogenic surf, federal outlooks hint at a gradual warming trend as December unfolds, even as forecasters keep half an eye on models suggesting a possible pattern shift later in the month. For now, the Bay Area’s forecast reads like a meteorological paradox: cold records, freeze warnings and flood advisories all wrapped inside an otherwise quiet, dry pattern—just another week in a state where even the weather insists on multitasking.
The Sources…
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- https://www.cbsnews.com/sanfrancisco/news/bay-area-coastal-flood-advisory-december-2025-king-tides/
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- https://x.com/joffemd/status/1995523814026031206
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- https://sfoskywarn.org/wp-content/uploads/2025/11/partneremail.pdf
