Oconomowoc Lake, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36.9 °F (low) to 56.2 °F (high). Annual precipitation averages 36.4 Inches. 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 | 11.1 °F | 27.2 °F | 1.65 in. |
| February | 13.7 °F | 30.8 °F | 1.6 in. |
| March | 23.8 °F | 42.5 °F | 2.05 in. |
| April | 35.1 °F | 55.7 °F | 3.76 in. |
| May | 46.4 °F | 67.7 °F | 4.12 in. |
| June | 56.4 °F | 77.5 °F | 4.86 in. |
| July | 60.8 °F | 81.6 °F | 4.09 in. |
| August | 59.0 °F | 79.9 °F | 4.03 in. |
| September | 50.9 °F | 73.1 °F | 3.32 in. |
| October | 39.6 °F | 59.9 °F | 2.87 in. |
| November | 28.4 °F | 45.3 °F | 2.17 in. |
| December | 17.9 °F | 32.7 °F | 1.89 in. |
| Annual | 36.9 °F | 56.2 °F | 36.41 in. |
| 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 : -15°F to -10°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 |