The official National Weather Service forecast for Napoleon — 41.3923°N, 84.1252°W, population 8,868, 17.5 miles from I-90.
| Henry County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 33 | 37 | 48 | 61 | 72 | 82 | 85 | 83 | 77 | 64 | 50 | 38 | 61 |
| Avg low °F | 19 | 21 | 30 | 39 | 50 | 60 | 63 | 61 | 54 | 44 | 33 | 25 | 42 |
| Precip in | 2.3 | 2.2 | 2.6 | 3.3 | 4.2 | 4.0 | 3.9 | 3.5 | 2.9 | 2.7 | 2.4 | 2.5 | 36.5 |
1996–2025 normals for Henry County — the climate division Napoleon sits in. All-time county record high 104.2°F (2012-06-29); record low -20.0°F (1994-01-19). Source: NOAA / National Weather Service.