Johnsonville, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 45.3 °F (low) to 65.5 °F (high). Annual precipitation averages 45.8 Inches. Johnsonville 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 22.7 °F | 38.9 °F | 3.31 in. |
| February | 25.7 °F | 43.7 °F | 2.62 in. |
| March | 34.3 °F | 54.2 °F | 3.8 in. |
| April | 44.6 °F | 66.3 °F | 4.97 in. |
| May | 55.4 °F | 75.9 °F | 4.97 in. |
| June | 64.3 °F | 84.7 °F | 4.87 in. |
| July | 67.3 °F | 87.6 °F | 4.03 in. |
| August | 64.9 °F | 86.7 °F | 3.41 in. |
| September | 56.8 °F | 80.9 °F | 3.3 in. |
| October | 45.5 °F | 69.3 °F | 3.43 in. |
| November | 35.2 °F | 54.6 °F | 3.97 in. |
| December | 27.2 °F | 43.1 °F | 3.13 in. |
| Annual | 45.3 °F | 65.5 °F | 45.81 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |