Rockford, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.8 °C (low) to 14.5 °C (high). Annual precipitation averages 957.1 Millimeters. Rockford 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 | -10.7 °C | -1.9 °C | 39.62 mm |
| February | -8.9 °C | 0.3 °C | 43.18 mm |
| March | -3.2 °C | 7.2 °C | 54.1 mm |
| April | 2.9 °C | 14.8 °C | 95 mm |
| May | 9.4 °C | 21.2 °C | 114.81 mm |
| June | 15 °C | 26.6 °C | 140.46 mm |
| July | 17.1 °C | 28.4 °C | 96.01 mm |
| August | 16.1 °C | 27.5 °C | 106.93 mm |
| September | 11.4 °C | 23.9 °C | 85.09 mm |
| October | 4.8 °C | 16.7 °C | 71.63 mm |
| November | -1.4 °C | 8.2 °C | 58.17 mm |
| December | -7.2 °C | 1.2 °C | 52.07 mm |
| Annual | 3.8 °C | 14.5 °C | 957.07 mm |
| 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 : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |