Casey, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 15.5 °C (high). Annual precipitation averages 903.7 Millimeters. Casey is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.1 °C | -0.9 °C | 21.08 mm |
| February | -8.9 °C | 1.8 °C | 28.96 mm |
| March | -3 °C | 9 °C | 50.04 mm |
| April | 3.1 °C | 16.2 °C | 93.47 mm |
| May | 9.9 °C | 22 °C | 131.57 mm |
| June | 15.7 °C | 27.3 °C | 131.32 mm |
| July | 17.7 °C | 29.3 °C | 105.92 mm |
| August | 16.3 °C | 28.3 °C | 103.12 mm |
| September | 11.3 °C | 24.8 °C | 89.92 mm |
| October | 4.4 °C | 17.7 °C | 70.36 mm |
| November | -2.4 °C | 9 °C | 44.7 mm |
| December | -8.1 °C | 1.8 °C | 33.27 mm |
| Annual | 3.7 °C | 15.5 °C | 903.73 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |