Assumption, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43.2 °F (low) to 63.8 °F (high). Annual precipitation averages 40.2 Inches. Assumption 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 19.6 °F | 35.9 °F | 2.26 in. |
| February | 22.7 °F | 40.9 °F | 2.03 in. |
| March | 31.8 °F | 52.0 °F | 2.79 in. |
| April | 42.4 °F | 64.9 °F | 4.37 in. |
| May | 53.6 °F | 75.1 °F | 4.74 in. |
| June | 62.4 °F | 83.5 °F | 4.98 in. |
| July | 65.3 °F | 86.5 °F | 3.61 in. |
| August | 63.2 °F | 85.3 °F | 2.96 in. |
| September | 55.1 °F | 80.3 °F | 3.32 in. |
| October | 43.8 °F | 68.0 °F | 3.34 in. |
| November | 33.3 °F | 52.5 °F | 3.34 in. |
| December | 25.0 °F | 40.7 °F | 2.46 in. |
| Annual | 43.2 °F | 63.8 °F | 40.2 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 6a : -10°F to -5°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 |