Monticello, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.2 °C (low) to 17.2 °C (high). Annual precipitation averages 1007.4 Millimeters. Monticello is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.8 °C | 1.6 °C | 41.4 mm |
| February | -5.9 °C | 4.2 °C | 48.01 mm |
| March | -0.4 °C | 10.9 °C | 62.99 mm |
| April | 5.7 °C | 17.8 °C | 100.84 mm |
| May | 11.9 °C | 23.2 °C | 133.35 mm |
| June | 17.4 °C | 28.3 °C | 122.17 mm |
| July | 19.3 °C | 30.4 °C | 107.44 mm |
| August | 18.1 °C | 29.6 °C | 98.81 mm |
| September | 13.4 °C | 25.9 °C | 94.74 mm |
| October | 6.9 °C | 19.1 °C | 85.6 mm |
| November | 0.6 °C | 11.1 °C | 63.75 mm |
| December | -4.8 °C | 4.1 °C | 48.26 mm |
| Annual | 6.2 °C | 17.2 °C | 1007.36 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |