Lake Mills, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.1 °C (low) to 12.8 °C (high). Annual precipitation averages 910.1 Millimeters. Lake Mills 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 | -14.2 °C | -4.8 °C | 25.15 mm |
| February | -11.7 °C | -2.2 °C | 26.16 mm |
| March | -4.9 °C | 4.7 °C | 49.28 mm |
| April | 1.7 °C | 13.4 °C | 97.28 mm |
| May | 8.7 °C | 20.3 °C | 127.76 mm |
| June | 14.7 °C | 25.8 °C | 139.7 mm |
| July | 16.4 °C | 27.6 °C | 116.33 mm |
| August | 14.9 °C | 26.3 °C | 103.63 mm |
| September | 10.1 °C | 22.8 °C | 86.11 mm |
| October | 3.2 °C | 15.4 °C | 62.23 mm |
| November | -3.5 °C | 6.2 °C | 42.42 mm |
| December | -10.3 °C | -1.7 °C | 34.04 mm |
| Annual | 2.1 °C | 12.8 °C | 910.09 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |