Harrison, Georgia has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.6 °C (low) to 24.4 °C (high). Annual precipitation averages 1214.7 Millimeters. Harrison 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. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.9 °C | 14.4 °C | 111.25 mm |
| February | 3.2 °C | 16.4 °C | 108.97 mm |
| March | 6.6 °C | 20.6 °C | 112.78 mm |
| April | 10.5 °C | 24.6 °C | 87.63 mm |
| May | 15.5 °C | 28.6 °C | 75.95 mm |
| June | 19.8 °C | 31.7 °C | 120.4 mm |
| July | 21.6 °C | 33.4 °C | 116.84 mm |
| August | 21.1 °C | 32.4 °C | 124.97 mm |
| September | 18.1 °C | 29.9 °C | 97.79 mm |
| October | 12.1 °C | 25 °C | 70.61 mm |
| November | 6 °C | 19.8 °C | 75.95 mm |
| December | 2.9 °C | 15.6 °C | 111.51 mm |
| Annual | 11.6 °C | 24.4 °C | 1214.65 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| 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 | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |