The official National Weather Service forecast for Santa Rosa — 38.4405°N, 122.7144°W, population 297,329, 33.5 miles from I-80. Forecasts here are written by NWS MTR, this county’s forecast office.
| Sonoma County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 57 | 59 | 62 | 66 | 71 | 77 | 80 | 81 | 80 | 73 | 63 | 57 | 69 |
| Avg low °F | 40 | 41 | 42 | 43 | 47 | 51 | 53 | 54 | 52 | 49 | 43 | 40 | 46 |
| Precip in | 7.6 | 7.8 | 5.3 | 2.7 | 1.3 | 0.2 | 0.0 | 0.0 | 0.2 | 2.1 | 4.8 | 9.2 | 41.2 |
1996–2025 normals for Sonoma County — the climate division Santa Rosa sits in. All-time county record high 105.9°F (2022-09-07); record low 16.1°F (1990-12-22). Source: NOAA / National Weather Service.