Hartwell, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.9 °F (low) to 66.2 °F (high). Annual precipitation averages 43.5 Inches. Hartwell is located in USDA Plant Hardiness Zone 6b. 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 | 20.7 °F | 40.2 °F | 1.7 in. |
| February | 24.5 °F | 45.4 °F | 1.98 in. |
| March | 33.7 °F | 56.0 °F | 2.85 in. |
| April | 43.5 °F | 66.3 °F | 4.6 in. |
| May | 54.8 °F | 75.5 °F | 5.62 in. |
| June | 64.5 °F | 84.3 °F | 5.23 in. |
| July | 68.4 °F | 89.1 °F | 4.62 in. |
| August | 66.2 °F | 88.1 °F | 4.03 in. |
| September | 57.4 °F | 80.4 °F | 4.36 in. |
| October | 45.2 °F | 69.2 °F | 3.44 in. |
| November | 34.2 °F | 55.5 °F | 2.94 in. |
| December | 25.2 °F | 44.3 °F | 2.15 in. |
| Annual | 44.9 °F | 66.2 °F | 43.52 in. |
| 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 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 |