Lewis, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 15.8 °C (high). Annual precipitation averages 886 Millimeters. Lewis 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 | -11.2 °C | -0.7 °C | 21.34 mm |
| February | -9 °C | 2.1 °C | 28.7 mm |
| March | -2.8 °C | 9.4 °C | 48.51 mm |
| April | 3 °C | 16.6 °C | 90.17 mm |
| May | 10 °C | 22.3 °C | 137.41 mm |
| June | 15.8 °C | 27.7 °C | 124.46 mm |
| July | 17.8 °C | 29.5 °C | 99.57 mm |
| August | 16.3 °C | 28.6 °C | 101.09 mm |
| September | 11 °C | 25.1 °C | 86.11 mm |
| October | 4.3 °C | 18.1 °C | 72.14 mm |
| November | -2.7 °C | 9.2 °C | 42.67 mm |
| December | -8.2 °C | 2.1 °C | 33.78 mm |
| Annual | 3.7 °C | 15.8 °C | 885.95 mm |
| 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 : -26.1°C to -23.3°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 |