Hartwell, Georgia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 10.6 °C (low) to 22.4 °C (high). Annual precipitation averages 1304 Millimeters. Hartwell is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.3 °C | 11.8 °C | 111.25 mm |
| February | 1.8 °C | 13.9 °C | 113.28 mm |
| March | 5.2 °C | 18.1 °C | 115.06 mm |
| April | 9.6 °C | 22.8 °C | 94.49 mm |
| May | 14.6 °C | 26.7 °C | 97.79 mm |
| June | 19.1 °C | 30.4 °C | 110.49 mm |
| July | 21 °C | 32.2 °C | 110.49 mm |
| August | 20.6 °C | 31.2 °C | 115.82 mm |
| September | 17.4 °C | 28.2 °C | 113.03 mm |
| October | 10.7 °C | 22.9 °C | 93.98 mm |
| November | 4.7 °C | 17.7 °C | 101.35 mm |
| December | 1.8 °C | 13.2 °C | 127 mm |
| Annual | 10.6 °C | 22.4 °C | 1304.03 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 40-50 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 | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |