Millbrook, Alabama has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.3 °C (low) to 24.8 °C (high). Annual precipitation averages 1412.5 Millimeters. Millbrook is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.3 °C | 14.4 °C | 132.08 mm |
| February | 4.1 °C | 16.9 °C | 137.92 mm |
| March | 7.7 °C | 21.1 °C | 134.62 mm |
| April | 11.3 °C | 25.1 °C | 114.05 mm |
| May | 16.3 °C | 29.2 °C | 105.66 mm |
| June | 20.6 °C | 32.2 °C | 128.27 mm |
| July | 22.3 °C | 33.4 °C | 129.79 mm |
| August | 21.9 °C | 33.2 °C | 108.97 mm |
| September | 19.1 °C | 31.1 °C | 98.04 mm |
| October | 12.5 °C | 25.8 °C | 77.98 mm |
| November | 6.2 °C | 20 °C | 104.9 mm |
| December | 3.6 °C | 15.6 °C | 140.21 mm |
| Annual | 12.3 °C | 24.8 °C | 1412.49 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 20-30 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 | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |