The official National Weather Service forecast for Oelwein — 42.6733°N, 91.9135°W, population 6,585, 21.1 miles from I-380.
| Fayette County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 25 | 30 | 44 | 58 | 70 | 79 | 82 | 80 | 74 | 61 | 45 | 31 | 57 |
| Avg low °F | 9 | 12 | 25 | 35 | 47 | 57 | 61 | 58 | 51 | 38 | 27 | 15 | 36 |
| Precip in | 1.1 | 1.2 | 2.0 | 3.6 | 4.9 | 6.0 | 4.7 | 4.2 | 3.5 | 2.9 | 1.8 | 1.5 | 37.4 |
1996–2025 normals for Fayette County — the climate division Oelwein sits in. All-time county record high 102.4°F (1988-08-18); record low -33.2°F (1996-02-03). Source: NOAA / National Weather Service.