Millen, Georgia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.9 °C (low) to 25.2 °C (high). Annual precipitation averages 1179.6 Millimeters. Millen 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 | 2.2 °C | 15.3 °C | 98.81 mm |
| February | 3.6 °C | 17.4 °C | 104.65 mm |
| March | 6.9 °C | 21.3 °C | 99.57 mm |
| April | 10.6 °C | 25.6 °C | 81.03 mm |
| May | 15.6 °C | 29.5 °C | 80.77 mm |
| June | 20.1 °C | 32.3 °C | 127 mm |
| July | 21.8 °C | 33.7 °C | 126.49 mm |
| August | 21.7 °C | 33.1 °C | 122.94 mm |
| September | 18.7 °C | 30.6 °C | 90.93 mm |
| October | 12.1 °C | 25.9 °C | 72.64 mm |
| November | 6.2 °C | 20.6 °C | 69.34 mm |
| December | 3.5 °C | 16.6 °C | 105.41 mm |
| Annual | 11.9 °C | 25.2 °C | 1179.58 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 |