Monticello, Mississippi has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.4 °C (low) to 25.6 °C (high). Annual precipitation averages 1535.7 Millimeters. Monticello is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.4 °C | 15.1 °C | 152.91 mm |
| February | 4.3 °C | 17.9 °C | 146.81 mm |
| March | 7.9 °C | 21.8 °C | 146.56 mm |
| April | 11.9 °C | 25.9 °C | 136.4 mm |
| May | 16.6 °C | 29.7 °C | 120.4 mm |
| June | 20.6 °C | 32.8 °C | 125.48 mm |
| July | 21.9 °C | 34.1 °C | 137.67 mm |
| August | 21.7 °C | 34.2 °C | 124.97 mm |
| September | 18.9 °C | 31.7 °C | 96.77 mm |
| October | 12.4 °C | 26.7 °C | 93.22 mm |
| November | 6.4 °C | 20.6 °C | 118.36 mm |
| December | 3.8 °C | 16.4 °C | 136.14 mm |
| Annual | 12.4 °C | 25.6 °C | 1535.69 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |