Rock Falls, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.3 °F (low) to 59.2 °F (high). Annual precipitation averages 39.4 Inches. Rock Falls 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.1 °F | 29.5 °F | 1.71 in. |
| February | 16.9 °F | 34.0 °F | 1.72 in. |
| March | 27.4 °F | 46.6 °F | 2.39 in. |
| April | 38.0 °F | 60.2 °F | 3.83 in. |
| May | 50.0 °F | 71.6 °F | 4.92 in. |
| June | 59.8 °F | 80.7 °F | 5.42 in. |
| July | 63.0 °F | 83.6 °F | 4.28 in. |
| August | 60.9 °F | 81.9 °F | 4.28 in. |
| September | 52.5 °F | 76.0 °F | 3.76 in. |
| October | 40.8 °F | 63.1 °F | 2.81 in. |
| November | 29.7 °F | 47.7 °F | 2.29 in. |
| December | 19.7 °F | 35.1 °F | 1.94 in. |
| Annual | 39.3 °F | 59.2 °F | 39.35 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |