| 2023 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| 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 53045 - Brookfield, WI | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 11 | 15 | 25 | 36 | 47 | 56 | 62 | 60 | 52 | 40 | 29 | 17 | 38 |
| Avg Max Temp (°F) | 27 | 32 | 42 | 55 | 68 | 78 | 82 | 80 | 72 | 60 | 45 | 32 | 56 |
| Avg Precip (In.) | 1.46 | 1.26 | 2.16 | 3.47 | 3.02 | 3.74 | 3.79 | 4.4 | 3.47 | 2.51 | 2.53 | 1.83 | 33.63 |