Oconomowoc Lake, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.7 °C (low) to 13.4 °C (high). Annual precipitation averages 924.8 Millimeters. Oconomowoc Lake is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.6 °C | -2.7 °C | 41.91 mm |
| February | -10.2 °C | -0.7 °C | 40.64 mm |
| March | -4.6 °C | 5.8 °C | 52.07 mm |
| April | 1.7 °C | 13.2 °C | 95.5 mm |
| May | 8 °C | 19.8 °C | 104.65 mm |
| June | 13.6 °C | 25.3 °C | 123.44 mm |
| July | 16 °C | 27.6 °C | 103.89 mm |
| August | 15 °C | 26.6 °C | 102.36 mm |
| September | 10.5 °C | 22.8 °C | 84.33 mm |
| October | 4.2 °C | 15.5 °C | 72.9 mm |
| November | -2 °C | 7.4 °C | 55.12 mm |
| December | -7.8 °C | 0.4 °C | 48.01 mm |
| Annual | 2.7 °C | 13.4 °C | 924.82 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |