The official National Weather Service forecast for Marengo — 40.4009°N, 82.8107°W, 1.7 miles from I-71.
| Morrow County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 34 | 38 | 49 | 62 | 72 | 80 | 83 | 82 | 76 | 64 | 50 | 39 | 61 |
| Avg low °F | 19 | 21 | 29 | 39 | 49 | 58 | 61 | 60 | 53 | 42 | 32 | 24 | 41 |
| Precip in | 2.8 | 2.5 | 3.1 | 3.9 | 4.6 | 4.6 | 4.0 | 3.7 | 3.5 | 3.1 | 2.8 | 3.2 | 41.8 |
1996–2025 normals for Morrow County — the climate division Marengo sits in. All-time county record high 101.0°F (1988-06-26); record low -25.2°F (1994-01-19). Source: NOAA / National Weather Service.