Lewis, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.6 °F (low) to 60.5 °F (high). Annual precipitation averages 34.9 Inches. 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 | 11.8 °F | 30.8 °F | 0.84 in. |
| February | 15.8 °F | 35.8 °F | 1.13 in. |
| March | 26.9 °F | 49.0 °F | 1.91 in. |
| April | 37.4 °F | 61.9 °F | 3.55 in. |
| May | 50.0 °F | 72.1 °F | 5.41 in. |
| June | 60.4 °F | 81.8 °F | 4.9 in. |
| July | 64.1 °F | 85.1 °F | 3.92 in. |
| August | 61.3 °F | 83.4 °F | 3.98 in. |
| September | 51.8 °F | 77.2 °F | 3.39 in. |
| October | 39.7 °F | 64.5 °F | 2.84 in. |
| November | 27.1 °F | 48.5 °F | 1.68 in. |
| December | 17.2 °F | 35.7 °F | 1.33 in. |
| Annual | 38.6 °F | 60.5 °F | 34.88 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 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |