The official National Weather Service forecast for Mount Vernon — 40.3934°N, 82.4857°W, population 18,993, 14.1 miles from I-71.
| Knox County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 35 | 39 | 50 | 62 | 72 | 80 | 83 | 82 | 76 | 64 | 51 | 40 | 61 |
| Avg low °F | 19 | 21 | 29 | 39 | 49 | 58 | 61 | 59 | 52 | 42 | 32 | 25 | 40 |
| Precip in | 2.9 | 2.6 | 3.4 | 4.0 | 4.6 | 4.7 | 4.0 | 3.6 | 3.4 | 3.0 | 2.8 | 3.2 | 42.2 |
1996–2025 normals for Knox County — the climate division Mount Vernon sits in. All-time county record high 100.0°F (1988-06-26); record low -26.7°F (1994-01-19). Source: NOAA / National Weather Service.