The official National Weather Service forecast for Lake Mills — 43.0814°N, 88.9118°W, population 6,857, 1.2 miles from I-94. Forecasts here are written by NWS MKX, this county’s forecast office.
| Jefferson County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 28 | 32 | 44 | 57 | 69 | 79 | 83 | 81 | 75 | 61 | 46 | 33 | 57 |
| Avg low °F | 13 | 15 | 25 | 35 | 47 | 57 | 61 | 59 | 52 | 40 | 29 | 19 | 38 |
| Precip in | 1.5 | 1.5 | 2.2 | 3.5 | 4.2 | 5.2 | 3.8 | 4.0 | 3.3 | 2.8 | 2.0 | 1.8 | 35.8 |
1996–2025 normals for Jefferson County — the climate division Lake Mills sits in. All-time county record high 103.4°F (2012-07-06); record low -31.8°F (1951-01-30). Source: NOAA / National Weather Service.