Smyrna, Georgia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 10.4 °C (low) to 21.7 °C (high). Annual precipitation averages 1365.8 Millimeters. Smyrna is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0 °C | 11.1 °C | 122.17 mm |
| February | 1.4 °C | 13.3 °C | 120.4 mm |
| March | 5.2 °C | 17.8 °C | 125.22 mm |
| April | 9.6 °C | 22.1 °C | 109.22 mm |
| May | 14.6 °C | 25.9 °C | 106.68 mm |
| June | 19 °C | 29.3 °C | 112.27 mm |
| July | 20.8 °C | 30.8 °C | 134.11 mm |
| August | 20.4 °C | 30.5 °C | 103.89 mm |
| September | 17.1 °C | 27.7 °C | 106.93 mm |
| October | 10.6 °C | 22.5 °C | 94.49 mm |
| November | 4.4 °C | 17 °C | 106.17 mm |
| December | 1.7 °C | 12.4 °C | 124.21 mm |
| Annual | 10.4 °C | 21.7 °C | 1365.76 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |