The official National Weather Service forecast for Monticello — 42.2383°N, 91.1871°W, 28 miles from I-380.
| Jones County | J | F | M | A | M | J | J | A | S | O | N | D | Year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 28 | 33 | 47 | 60 | 71 | 81 | 83 | 81 | 76 | 63 | 47 | 33 | 59 |
| Avg low °F | 12 | 15 | 27 | 37 | 49 | 59 | 63 | 60 | 53 | 40 | 29 | 18 | 38 |
| Precip in | 1.3 | 1.4 | 2.2 | 3.8 | 4.6 | 5.7 | 4.5 | 4.0 | 3.2 | 3.3 | 1.9 | 1.8 | 37.7 |
1996–2025 normals for Jones County — the climate division Monticello sits in. All-time county record high 102.2°F (2012-07-26); record low -32.9°F (2009-01-16). Source: NOAA / National Weather Service.