The official National Weather Service forecast for Marysville — 42.9125°N, 82.4869°W, 1.4 miles from I-94. Forecasts here are written by NWS DTX, this county’s forecast office.
| St. Clair County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 31 | 34 | 44 | 56 | 68 | 78 | 82 | 80 | 74 | 61 | 48 | 36 | 58 |
| Avg low °F | 18 | 19 | 27 | 37 | 47 | 58 | 62 | 61 | 55 | 44 | 34 | 25 | 41 |
| Precip in | 2.2 | 2.0 | 2.3 | 3.1 | 3.6 | 3.4 | 3.3 | 3.3 | 3.1 | 2.9 | 2.3 | 2.4 | 33.9 |
1996–2025 normals for St. Clair County — the climate division Marysville sits in. All-time county record high 99.3°F (1988-07-08); record low -18.0°F (1994-01-19). Source: NOAA / National Weather Service.