The official National Weather Service forecast for Oskaloosa — 39.2153°N, 95.3127°W, 15.8 miles from I-70.
| Jefferson County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 39 | 44 | 56 | 66 | 75 | 85 | 89 | 88 | 81 | 68 | 55 | 43 | 66 |
| Avg low °F | 19 | 22 | 33 | 43 | 54 | 64 | 68 | 66 | 57 | 45 | 33 | 23 | 44 |
| Precip in | 1.0 | 1.3 | 2.2 | 3.5 | 5.1 | 5.2 | 4.0 | 4.5 | 3.2 | 3.1 | 1.8 | 1.4 | 36.3 |
1996–2025 normals for Jefferson County — the climate division Oskaloosa sits in. All-time county record high 109.4°F (1980-07-15); record low -22.3°F (1989-12-23). Source: NOAA / National Weather Service.