Island Lake, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.9 °F (low) to 58 °F (high). Annual precipitation averages 38.3 Inches. Island Lake is located in USDA Plant Hardiness Zone 5b. 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 | 13.9 °F | 29.5 °F | 1.84 in. |
| February | 16.7 °F | 33.5 °F | 1.88 in. |
| March | 26.3 °F | 44.8 °F | 2.24 in. |
| April | 36.6 °F | 57.6 °F | 3.78 in. |
| May | 47.6 °F | 69.0 °F | 4.76 in. |
| June | 57.7 °F | 78.9 °F | 4.85 in. |
| July | 62.5 °F | 83.1 °F | 3.93 in. |
| August | 61.0 °F | 81.2 °F | 3.92 in. |
| September | 53.0 °F | 74.4 °F | 3.52 in. |
| October | 41.1 °F | 61.5 °F | 3.16 in. |
| November | 30.3 °F | 47.1 °F | 2.42 in. |
| December | 20.1 °F | 34.9 °F | 2.04 in. |
| Annual | 38.9 °F | 58 °F | 38.34 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |