Berwyn, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.9 °F (low) to 59.5 °F (high). Annual precipitation averages 39.6 Inches. Berwyn 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 | 18.1 °F | 31.9 °F | 2.17 in. |
| February | 20.8 °F | 35.6 °F | 2.07 in. |
| March | 29.9 °F | 46.3 °F | 2.35 in. |
| April | 40.2 °F | 58.7 °F | 3.97 in. |
| May | 51.2 °F | 69.9 °F | 4.71 in. |
| June | 61.4 °F | 79.9 °F | 4.34 in. |
| July | 66.7 °F | 84.3 °F | 4.3 in. |
| August | 65.5 °F | 82.4 °F | 4.11 in. |
| September | 58.0 °F | 76.0 °F | 3.26 in. |
| October | 45.6 °F | 63.2 °F | 3.43 in. |
| November | 34.0 °F | 48.9 °F | 2.55 in. |
| December | 23.8 °F | 37.2 °F | 2.32 in. |
| Annual | 42.9 °F | 59.5 °F | 39.58 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 6a : -10°F to -5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |