Atlanta, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.5 °C (low) to 16.8 °C (high). Annual precipitation averages 989.6 Millimeters. Atlanta is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.2 °C | 0.9 °C | 56.64 mm |
| February | -6.4 °C | 3.7 °C | 50.55 mm |
| March | -1.2 °C | 10.2 °C | 68.07 mm |
| April | 4.8 °C | 17.4 °C | 97.28 mm |
| May | 11.3 °C | 23.2 °C | 112.01 mm |
| June | 16.5 °C | 28.2 °C | 112.52 mm |
| July | 18.2 °C | 29.8 °C | 105.16 mm |
| August | 17.1 °C | 28.8 °C | 89.92 mm |
| September | 12.6 °C | 26.1 °C | 82.55 mm |
| October | 6.1 °C | 18.8 °C | 83.57 mm |
| November | 0 °C | 10.6 °C | 72.64 mm |
| December | -5.1 °C | 3.8 °C | 58.67 mm |
| Annual | 5.5 °C | 16.8 °C | 989.58 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |