The official National Weather Service forecast for San Ramon — 37.7799°N, 121.978°W, 3.2 miles from I-680. Forecasts here are written by NWS MTR, this county’s forecast office.
| Contra Costa County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 56 | 60 | 65 | 69 | 76 | 82 | 86 | 86 | 84 | 76 | 64 | 56 | 72 |
| Avg low °F | 41 | 42 | 44 | 47 | 51 | 56 | 58 | 58 | 57 | 52 | 45 | 41 | 49 |
| Precip in | 3.7 | 3.5 | 2.6 | 1.3 | 0.6 | 0.1 | 0.0 | 0.0 | 0.1 | 1.0 | 2.0 | 4.0 | 18.9 |
1996–2025 normals for Contra Costa County — the climate division San Ramon sits in. All-time county record high 109.7°F (2022-09-07); record low 18.5°F (1990-12-22). Source: NOAA / National Weather Service.