The official National Weather Service forecast for Marion — 42.0342°N, 91.5977°W, 4.1 miles from I-380.
| Linn County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 28 | 33 | 47 | 60 | 71 | 81 | 84 | 82 | 76 | 63 | 47 | 34 | 59 |
| Avg low °F | 11 | 15 | 27 | 37 | 49 | 59 | 63 | 60 | 52 | 40 | 28 | 17 | 38 |
| Precip in | 1.2 | 1.3 | 2.1 | 3.7 | 4.5 | 5.6 | 4.1 | 4.0 | 3.2 | 3.2 | 1.9 | 1.6 | 36.4 |
1996–2025 normals for Linn County — the climate division Marion sits in. All-time county record high 103.9°F (2012-07-26); record low -32.6°F (2019-01-31). Source: NOAA / National Weather Service.