Brighton, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.4 °C (low) to 18 °C (high). Annual precipitation averages 1059.9 Millimeters. Brighton is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.8 °C | 3.1 °C | 63.5 mm |
| February | -3.9 °C | 6.2 °C | 56.39 mm |
| March | 1.1 °C | 11.9 °C | 82.04 mm |
| April | 7 °C | 18.4 °C | 117.86 mm |
| May | 13.1 °C | 23.7 °C | 129.79 mm |
| June | 18.1 °C | 28.5 °C | 104.65 mm |
| July | 20 °C | 30.2 °C | 94.74 mm |
| August | 18.9 °C | 29.7 °C | 92.71 mm |
| September | 14.2 °C | 26.3 °C | 83.82 mm |
| October | 7.8 °C | 19.8 °C | 82.8 mm |
| November | 1.7 °C | 11.9 °C | 85.34 mm |
| December | -3.2 °C | 5.8 °C | 66.29 mm |
| Annual | 7.4 °C | 18 °C | 1059.93 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |