The official National Weather Service forecast for Marshalltown — 42.0494°N, 92.908°W, population 27,381, 25.5 miles from I-80.
| Marshall 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 | 77 | 63 | 48 | 34 | 59 |
| Avg low °F | 11 | 15 | 27 | 37 | 49 | 60 | 63 | 60 | 53 | 40 | 29 | 17 | 38 |
| Precip in | 1.0 | 1.0 | 1.9 | 3.5 | 5.0 | 5.4 | 4.1 | 3.9 | 3.0 | 2.9 | 1.7 | 1.4 | 34.8 |
1996–2025 normals for Marshall County — the climate division Marshalltown sits in. All-time county record high 103.0°F (1988-08-16); record low -29.7°F (1996-02-03). Source: NOAA / National Weather Service.