River Grove, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.4 °F (low) to 59.2 °F (high). Annual precipitation averages 38.8 Inches. River Grove is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.7 °F | 31.5 °F | 2.15 in. |
| February | 20.4 °F | 35.3 °F | 2.08 in. |
| March | 29.6 °F | 46.1 °F | 2.31 in. |
| April | 39.8 °F | 58.2 °F | 3.95 in. |
| May | 50.7 °F | 69.6 °F | 4.64 in. |
| June | 60.9 °F | 79.6 °F | 4.35 in. |
| July | 66.3 °F | 84.1 °F | 3.78 in. |
| August | 64.9 °F | 82.2 °F | 4.0 in. |
| September | 56.9 °F | 75.6 °F | 3.3 in. |
| October | 44.6 °F | 62.8 °F | 3.4 in. |
| November | 33.2 °F | 48.8 °F | 2.56 in. |
| December | 23.4 °F | 37.0 °F | 2.27 in. |
| Annual | 42.4 °F | 59.2 °F | 38.79 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |