Brimfield, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.4 °C (low) to 16 °C (high). Annual precipitation averages 971.8 Millimeters. Brimfield is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.8 °C | -0.3 °C | 49.78 mm |
| February | -7.8 °C | 2.3 °C | 50.04 mm |
| March | -2.2 °C | 9.4 °C | 62.99 mm |
| April | 3.7 °C | 16.8 °C | 94.23 mm |
| May | 10.4 °C | 22.8 °C | 125.98 mm |
| June | 15.8 °C | 27.6 °C | 114.81 mm |
| July | 17.6 °C | 29.2 °C | 101.09 mm |
| August | 16.3 °C | 28.3 °C | 90.42 mm |
| September | 11.7 °C | 25.2 °C | 91.95 mm |
| October | 5.2 °C | 18.2 °C | 75.18 mm |
| November | -1.1 °C | 9.8 °C | 64.52 mm |
| December | -6.5 °C | 2.7 °C | 50.8 mm |
| Annual | 4.4 °C | 16 °C | 971.79 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |