Brookfield, Wisconsin has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.2 °C (low) to 13.5 °C (high). Annual precipitation averages 904.8 Millimeters. Brookfield 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.8 °C | -2.1 °C | 43.69 mm |
| February | -9.2 °C | -0.1 °C | 40.89 mm |
| March | -4.1 °C | 6 °C | 51.05 mm |
| April | 1.9 °C | 12.9 °C | 97.54 mm |
| May | 7.9 °C | 19.4 °C | 102.11 mm |
| June | 13.4 °C | 24.9 °C | 121.41 mm |
| July | 16.3 °C | 27.6 °C | 97.79 mm |
| August | 15.5 °C | 26.7 °C | 95 mm |
| September | 10.9 °C | 22.8 °C | 80.01 mm |
| October | 4.7 °C | 15.7 °C | 71.63 mm |
| November | -1.4 °C | 7.7 °C | 52.58 mm |
| December | -7.2 °C | 0.9 °C | 51.05 mm |
| Annual | 3.2 °C | 13.5 °C | 904.75 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |