The official National Weather Service forecast for Lake Mills — 43.4194°N, 93.5333°W, 10.6 miles from I-35.
| Winnebago County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 24 | 28 | 42 | 57 | 69 | 79 | 82 | 79 | 74 | 60 | 44 | 29 | 56 |
| Avg low °F | 8 | 11 | 24 | 35 | 47 | 58 | 61 | 58 | 51 | 38 | 26 | 14 | 36 |
| Precip in | 0.9 | 1.0 | 1.9 | 3.5 | 4.7 | 5.1 | 4.3 | 4.1 | 3.2 | 2.4 | 1.4 | 1.2 | 33.7 |
1996–2025 normals for Winnebago County — the climate division Lake Mills sits in. All-time county record high 101.9°F (1985-06-09); record low -30.0°F (1996-02-02). Source: NOAA / National Weather Service.