The official National Weather Service forecast for Napa — 38.2971°N, 122.2855°W, population 84,619, 10 miles from I-80. Forecasts here are written by NWS MTR, this county’s forecast office.
| Napa County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 57 | 60 | 64 | 69 | 77 | 84 | 89 | 89 | 86 | 77 | 64 | 56 | 73 |
| Avg low °F | 39 | 40 | 41 | 44 | 49 | 54 | 57 | 57 | 55 | 49 | 43 | 39 | 47 |
| Precip in | 5.9 | 6.1 | 4.1 | 1.9 | 1.0 | 0.1 | 0.0 | 0.0 | 0.1 | 1.5 | 3.4 | 6.8 | 30.9 |
1996–2025 normals for Napa County — the climate division Napa sits in. All-time county record high 110.6°F (1972-07-15); record low 14.8°F (1990-12-22). Source: NOAA / National Weather Service.