Shirley, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.3 °F (low) to 61.8 °F (high). Annual precipitation averages 39.2 Inches. Shirley is located in USDA Plant Hardiness Zone 6a. 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 | 16.3 °F | 32.7 °F | 2.29 in. |
| February | 19.7 °F | 37.7 °F | 1.96 in. |
| March | 29.1 °F | 49.7 °F | 2.7 in. |
| April | 40.0 °F | 63.0 °F | 3.84 in. |
| May | 51.5 °F | 73.7 °F | 4.52 in. |
| June | 61.1 °F | 82.5 °F | 4.32 in. |
| July | 64.2 °F | 85.7 °F | 3.93 in. |
| August | 62.2 °F | 83.7 °F | 3.71 in. |
| September | 54.4 °F | 78.7 °F | 3.34 in. |
| October | 42.8 °F | 65.5 °F | 3.37 in. |
| November | 31.6 °F | 50.6 °F | 2.81 in. |
| December | 22.1 °F | 37.9 °F | 2.36 in. |
| Annual | 41.3 °F | 61.8 °F | 39.15 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 6a : -10°F to -5°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 |