Grand Ridge, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.7 °F (low) to 60.5 °F (high). Annual precipitation averages 37.9 Inches. Grand Ridge is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.7 °F | 31.5 °F | 1.96 in. |
| February | 19.1 °F | 35.9 °F | 1.82 in. |
| March | 28.6 °F | 48.3 °F | 2.5 in. |
| April | 39.1 °F | 61.5 °F | 3.56 in. |
| May | 50.9 °F | 72.5 °F | 4.64 in. |
| June | 60.6 °F | 81.4 °F | 4.53 in. |
| July | 64.1 °F | 84.3 °F | 3.91 in. |
| August | 61.9 °F | 82.4 °F | 3.8 in. |
| September | 53.9 °F | 77.2 °F | 3.4 in. |
| October | 42.2 °F | 64.6 °F | 3.07 in. |
| November | 31.2 °F | 49.4 °F | 2.63 in. |
| December | 21.3 °F | 36.7 °F | 2.08 in. |
| Annual | 40.7 °F | 60.5 °F | 37.9 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |