Franklin Grove, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.5 °F (low) to 58.4 °F (high). Annual precipitation averages 38.3 Inches. Franklin Grove is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.6 °F | 28.7 °F | 1.73 in. |
| February | 16.3 °F | 33.1 °F | 1.73 in. |
| March | 26.6 °F | 45.6 °F | 2.35 in. |
| April | 37.0 °F | 59.5 °F | 3.6 in. |
| May | 49.0 °F | 70.8 °F | 4.84 in. |
| June | 58.9 °F | 79.9 °F | 5.24 in. |
| July | 62.2 °F | 82.7 °F | 4.21 in. |
| August | 60.1 °F | 81.1 °F | 3.96 in. |
| September | 51.7 °F | 75.3 °F | 3.55 in. |
| October | 40.0 °F | 62.3 °F | 2.8 in. |
| November | 29.2 °F | 47.1 °F | 2.31 in. |
| December | 18.9 °F | 34.3 °F | 1.98 in. |
| Annual | 38.5 °F | 58.4 °F | 38.3 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |