Cullom, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.6 °F (low) to 61.2 °F (high). Annual precipitation averages 38.4 Inches. Cullom 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 | 16.1 °F | 32.3 °F | 2.2 in. |
| February | 19.2 °F | 36.8 °F | 1.88 in. |
| March | 28.7 °F | 48.9 °F | 2.57 in. |
| April | 39.0 °F | 62.4 °F | 3.74 in. |
| May | 50.8 °F | 73.4 °F | 4.49 in. |
| June | 60.4 °F | 82.1 °F | 4.48 in. |
| July | 63.6 °F | 84.8 °F | 4.33 in. |
| August | 61.2 °F | 83.2 °F | 3.68 in. |
| September | 53.1 °F | 78.1 °F | 3.05 in. |
| October | 41.8 °F | 65.4 °F | 3.22 in. |
| November | 31.3 °F | 50.1 °F | 2.71 in. |
| December | 21.6 °F | 37.3 °F | 2.07 in. |
| Annual | 40.6 °F | 61.2 °F | 38.42 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 |