| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 53b - Kettle Moraines |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 53066 - Oconomowoc, WI | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 8 | 13 | 24 | 36 | 47 | 56 | 61 | 59 | 50 | 39 | 27 | 15 | 36 |
| Avg Max Temp (°F) | 26 | 31 | 42 | 56 | 69 | 78 | 82 | 79 | 72 | 60 | 44 | 31 | 56 |
| Avg Precip (In.) | 1.31 | 1.2 | 2.01 | 3.25 | 3.14 | 3.96 | 4.14 | 4.4 | 3.64 | 2.59 | 2.32 | 1.68 | 33.63 |