Oconee, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.6 °F (low) to 64.1 °F (high). Annual precipitation averages 41.7 Inches. Oconee is located in USDA Plant Hardiness Zone 6b. 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 | 20.1 °F | 36.1 °F | 2.63 in. |
| February | 23.4 °F | 41.3 °F | 2.17 in. |
| March | 32.4 °F | 52.3 °F | 3.02 in. |
| April | 42.7 °F | 65.2 °F | 4.57 in. |
| May | 53.8 °F | 75.1 °F | 4.77 in. |
| June | 62.7 °F | 83.8 °F | 4.71 in. |
| July | 65.8 °F | 86.9 °F | 3.94 in. |
| August | 63.4 °F | 85.7 °F | 3.2 in. |
| September | 55.6 °F | 80.4 °F | 3.2 in. |
| October | 44.3 °F | 68.0 °F | 3.44 in. |
| November | 33.8 °F | 52.9 °F | 3.49 in. |
| December | 25.4 °F | 41.0 °F | 2.58 in. |
| Annual | 43.6 °F | 64.1 °F | 41.72 in. |
| 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 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 |