Sullivan, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 45.2 °F (low) to 66.1 °F (high). Annual precipitation averages 44.8 Inches. Sullivan is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 22.0 °F | 40.7 °F | 2.64 in. |
| February | 25.3 °F | 45.8 °F | 2.56 in. |
| March | 33.8 °F | 55.6 °F | 3.71 in. |
| April | 44.6 °F | 67.3 °F | 4.96 in. |
| May | 54.7 °F | 75.7 °F | 5.18 in. |
| June | 63.4 °F | 83.6 °F | 4.35 in. |
| July | 67.4 °F | 87.9 °F | 4.19 in. |
| August | 65.6 °F | 87.2 °F | 3.94 in. |
| September | 57.7 °F | 80.1 °F | 3.72 in. |
| October | 46.1 °F | 68.9 °F | 3.35 in. |
| November | 35.2 °F | 55.5 °F | 3.6 in. |
| December | 26.5 °F | 44.6 °F | 2.63 in. |
| Annual | 45.2 °F | 66.1 °F | 44.83 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |