Brighton, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 45.4 °F (low) to 64.3 °F (high). Annual precipitation averages 41.7 Inches. 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 | 21.6 °F | 37.6 °F | 2.5 in. |
| February | 25.0 °F | 43.1 °F | 2.22 in. |
| March | 33.9 °F | 53.5 °F | 3.23 in. |
| April | 44.6 °F | 65.2 °F | 4.64 in. |
| May | 55.5 °F | 74.6 °F | 5.11 in. |
| June | 64.6 °F | 83.3 °F | 4.12 in. |
| July | 68.0 °F | 86.4 °F | 3.73 in. |
| August | 66.1 °F | 85.5 °F | 3.65 in. |
| September | 57.6 °F | 79.3 °F | 3.3 in. |
| October | 46.1 °F | 67.6 °F | 3.26 in. |
| November | 35.1 °F | 53.5 °F | 3.36 in. |
| December | 26.3 °F | 42.4 °F | 2.61 in. |
| Annual | 45.4 °F | 64.3 °F | 41.73 in. |
| 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 : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |