Franklin, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.4 °C (low) to 17.4 °C (high). Annual precipitation averages 999.7 Millimeters. Franklin 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 | -7.1 °C | 1.8 °C | 53.85 mm |
| February | -5.1 °C | 4.7 °C | 49.02 mm |
| March | -0.1 °C | 11 °C | 71.88 mm |
| April | 5.8 °C | 18.1 °C | 106.93 mm |
| May | 12.2 °C | 23.6 °C | 120.9 mm |
| June | 17.3 °C | 28.2 °C | 118.87 mm |
| July | 19.1 °C | 29.8 °C | 97.79 mm |
| August | 17.8 °C | 29.3 °C | 84.07 mm |
| September | 13.2 °C | 26.5 °C | 85.09 mm |
| October | 6.8 °C | 19.5 °C | 78.49 mm |
| November | 0.9 °C | 11.2 °C | 77.22 mm |
| December | -4.1 °C | 4.7 °C | 55.63 mm |
| Annual | 6.4 °C | 17.4 °C | 999.74 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |