The official National Weather Service forecast for Hannibal — 39.6673°N, 80.872°W, 28.5 miles from I-70.
| Monroe County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 38 | 42 | 53 | 65 | 74 | 81 | 84 | 83 | 78 | 66 | 53 | 43 | 63 |
| Avg low °F | 21 | 24 | 31 | 40 | 49 | 58 | 62 | 61 | 54 | 43 | 33 | 26 | 42 |
| Precip in | 3.6 | 3.1 | 3.7 | 4.1 | 4.6 | 4.8 | 4.5 | 3.9 | 3.6 | 3.2 | 2.9 | 3.6 | 45.6 |
1996–2025 normals for Monroe County — the climate division Hannibal sits in. All-time county record high 99.9°F (1988-07-17); record low -25.7°F (1994-01-19). Source: NOAA / National Weather Service.