Rock Valley, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.3 °C (low) to 14.5 °C (high). Annual precipitation averages 727.5 Millimeters. Rock Valley is located in USDA Plant Hardiness Zone 5a. 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 | -13.3 °C | -3 °C | 14.99 mm |
| February | -10.8 °C | -0.2 °C | 19.81 mm |
| March | -4.6 °C | 6.9 °C | 38.35 mm |
| April | 1.7 °C | 15.1 °C | 74.42 mm |
| May | 8.7 °C | 21.8 °C | 100.33 mm |
| June | 14.9 °C | 27.4 °C | 119.13 mm |
| July | 16.8 °C | 29.3 °C | 82.8 mm |
| August | 15.3 °C | 28 °C | 84.33 mm |
| September | 10.1 °C | 24.4 °C | 73.91 mm |
| October | 2.9 °C | 16.8 °C | 62.99 mm |
| November | -4.3 °C | 7.3 °C | 34.04 mm |
| December | -10.2 °C | -0.4 °C | 22.35 mm |
| Annual | 2.3 °C | 14.5 °C | 727.45 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |