Lake Mills, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 35.8 °F (low) to 55.1 °F (high). Annual precipitation averages 35.8 Inches. 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 | 6.5 °F | 23.3 °F | 0.99 in. |
| February | 10.9 °F | 28.1 °F | 1.03 in. |
| March | 23.2 °F | 40.4 °F | 1.94 in. |
| April | 35.0 °F | 56.2 °F | 3.83 in. |
| May | 47.6 °F | 68.6 °F | 5.03 in. |
| June | 58.4 °F | 78.4 °F | 5.5 in. |
| July | 61.6 °F | 81.6 °F | 4.58 in. |
| August | 58.9 °F | 79.3 °F | 4.08 in. |
| September | 50.2 °F | 73.1 °F | 3.39 in. |
| October | 37.7 °F | 59.7 °F | 2.45 in. |
| November | 25.7 °F | 43.1 °F | 1.67 in. |
| December | 13.4 °F | 29.0 °F | 1.34 in. |
| Annual | 35.8 °F | 55.1 °F | 35.83 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |