San Francisco experienced an unusually cold day on Friday, marking its chilliest fall temperature in six years. The sudden drop surprised many residents who are used to mild November afternoons in the city.
A Rare Cold Day in San Francisco
According to the National Weather Service, the official high temperature in San Francisco reached only 52°F. This made it the coldest fall day since November 2019.
The main reason behind the sudden chill was a strong temperature inversion — a weather pattern that traps cold air close to the ground and prevents warmer air from mixing in.
How Fog and Inversion Made the Day Even Colder
A thick layer of fog settled over the city early in the morning. Because of the inversion, the fog never lifted, and the sun couldn’t warm the city as it normally does.
This kept temperatures stuck in the low 50s throughout the day, making the city feel even colder than usual for late November.
A Tale of Two Seasons: Coast vs. Mountains
While San Francisco shivered all day, the mountains told a very different weather story.
- South Lake Tahoe hit 59°F on Thanksgiving — the warmest this late in the year since 2017.
- On Friday, Tahoe stayed mild too, reaching 57°F.
This contrast happened because the inversion kept cold air near the coast but allowed warm sunshine in higher elevations.
The Cold Snap Reached Beyond the Bay Area
It wasn’t just San Francisco feeling the chill. Sacramento recorded its coldest November day in more than 30 years, showing how widespread the cold pattern was across Northern California.
Why This Weather Pattern Happened
Meteorologists say this cold spell is part of a slow, stagnant weather system sitting over the region. It creates quiet conditions that are perfect for fog but not for warm daytime temperatures.
Other Areas Stayed Warmer
Across the Bay Area, most cities saw highs in the upper 50s or low 60s — still cool, but not as cold as San Francisco. The city stood out because the inversion anchored the fog right over it.
What’s Next for the Weather?
The National Weather Service says the upcoming week will bring calm, mild, and quiet weather. Many areas will enjoy sunshine and pleasant conditions.
However, some inland valleys — especially in the East Bay and North Bay — may continue to deal with thick tule fog, which often forms overnight and early in the morning.
Will It Rain Soon?
The chance of rain remains uncertain. A possible weather system may arrive just beyond next week, but forecasters say there is still “high uncertainty” about whether the Bay Area will get any significant rainfall.
Conclusion
San Francisco’s coldest fall day in six years was caused by a rare combination of fog and a strong temperature inversion that kept warm air away. While the mountains enjoyed unusually warm weather, the city experienced a sharp and surprising chill. As the region moves into December, conditions are expected to stay calm with only a slight chance of rain on the horizon.
