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Measurable snow is rare in Vallejo: the 1991–2020 normal rounds to zero — only a trace in most years, and nights reach freezing on about 34 days a year. When snow or ice does arrive, it causes outsized trouble because roads are rarely treated — watch for Winter Weather Advisories and Freeze Warnings.
| Month | Snowfall | Days 1″+ | Days with snow cover | Freezing nights | Avg. low |
|---|---|---|---|---|---|
| November | 0″ | 0 | 0 | 5 | 40°F |
| December | 0″ | 0 | 0 | 11 | 38°F |
| January | 0″ | 0 | 0 | 9 | 38°F |
| February | 0″ | 0 | 0 | 5 | 40°F |
| March | 0″ | 0 | 0 | 2 | 42°F |
| April | 0″ | 0 | 0 | 1 | 44°F |
| Year | 0″ | 0 | 0 | 34 |
NOAA NCEI U.S. Climate Normals 1991–2020 — snowfall at Martinez Wtp (10 mi from the city center, -33 ft elevation difference); temperatures at Napa Co Airport. Averages smooth out big years: single winters can bring half or double the normal.
All California winter alerts and cities → · National winter storm map → · Frost dates by ZIP code →
0 inches in an average year (NOAA U.S. Climate Normals 1991–2020, Martinez Wtp station, 10 miles away).
This page checks the National Weather Service for active alerts at Vallejo's location every time you open it; the box at the top lists any winter storm, winter weather, cold or freeze alert in effect right now.
About 34 nights a year drop to 32 °F or below (NOAA 1991–2020); the coldest month, December, averages a low of 38 °F.