Countryside, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.9 °F (low) to 60.2 °F (high). Annual precipitation averages 39.9 Inches. Countryside 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.2 °F | 32.0 °F | 2.21 in. |
| February | 19.9 °F | 35.8 °F | 2.1 in. |
| March | 29.3 °F | 47.0 °F | 2.38 in. |
| April | 39.7 °F | 59.8 °F | 3.98 in. |
| May | 50.5 °F | 71.0 °F | 4.84 in. |
| June | 60.6 °F | 81.0 °F | 4.44 in. |
| July | 65.6 °F | 85.5 °F | 4.14 in. |
| August | 64.3 °F | 83.4 °F | 4.17 in. |
| September | 56.4 °F | 76.9 °F | 3.25 in. |
| October | 44.0 °F | 63.6 °F | 3.5 in. |
| November | 32.8 °F | 49.1 °F | 2.54 in. |
| December | 22.9 °F | 37.0 °F | 2.32 in. |
| Annual | 41.9 °F | 60.2 °F | 39.87 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |