Rockwell City, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.9 °C (low) to 14.2 °C (high). Annual precipitation averages 841.3 Millimeters. Rockwell City 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.8 °C | -3.1 °C | 19.3 mm |
| February | -10.6 °C | -0.6 °C | 25.15 mm |
| March | -3.9 °C | 7.2 °C | 49.28 mm |
| April | 2.2 °C | 15.1 °C | 91.69 mm |
| May | 9.2 °C | 21.2 °C | 124.97 mm |
| June | 15.3 °C | 26.8 °C | 130.81 mm |
| July | 17.2 °C | 28.4 °C | 91.44 mm |
| August | 15.8 °C | 27.1 °C | 102.11 mm |
| September | 10.7 °C | 23.9 °C | 74.68 mm |
| October | 3.8 °C | 16.7 °C | 62.48 mm |
| November | -3.3 °C | 7.5 °C | 35.81 mm |
| December | -9.3 °C | -0.1 °C | 33.53 mm |
| Annual | 2.9 °C | 14.2 °C | 841.25 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 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 |