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Central Valley Fog Traps Residents in Cold
13 Dec, 2025
Summary
- A 450-mile-long tule fog bank has persisted for weeks.
- Unusual weather factors and temperature inversion cause persistence.
- Fog has lowered temperatures, impacting visibility on roads.
An enormous fog formation, known as tule fog, has been lingering over central California for weeks, creating dreary conditions and colder-than-usual temperatures for residents. NASA satellite images reveal the impressive scope of this 450-mile-long anomaly that first appeared in November and has persisted into December.
The unique bowl-like shape of the Central Valley, combined with a temperature inversion where warmer air traps cold, moist air near the ground, allows the fog to become trapped. This persistent fog bank is considered extreme, as tule fog typically dissipates within a week.
Climate scientists point to warmer overall conditions, fueled by warm ocean waters offshore and a diminished snowpack in the Sierra Nevadas, as key factors allowing this unusually prolonged fog. The National Weather Service has issued dense fog advisories, warning of sudden drops in visibility on mountain roads due to the lingering tule fog.
