Crystal Lake, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.1 °C (low) to 12.9 °C (high). Annual precipitation averages 860.8 Millimeters. Crystal Lake is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.1 °C | -4.6 °C | 22.1 mm |
| February | -11.6 °C | -2.1 °C | 24.13 mm |
| March | -4.8 °C | 4.9 °C | 50.04 mm |
| April | 1.7 °C | 13.6 °C | 94.23 mm |
| May | 8.6 °C | 20.5 °C | 119.89 mm |
| June | 14.6 °C | 25.9 °C | 132.33 mm |
| July | 16.4 °C | 27.6 °C | 108.71 mm |
| August | 14.9 °C | 26.3 °C | 97.79 mm |
| September | 10.1 °C | 22.9 °C | 80.52 mm |
| October | 3.1 °C | 15.6 °C | 58.67 mm |
| November | -3.7 °C | 6.2 °C | 40.39 mm |
| December | -10.3 °C | -1.5 °C | 32 mm |
| Annual | 2.1 °C | 12.9 °C | 860.8 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |