Castana, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.2 °C (low) to 15.7 °C (high). Annual precipitation averages 810.5 Millimeters. Castana 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.9 °C | -1.2 °C | 17.27 mm |
| February | -9.6 °C | 1.7 °C | 21.34 mm |
| March | -3.4 °C | 9 °C | 40.89 mm |
| April | 2.6 °C | 16.5 °C | 89.92 mm |
| May | 9.4 °C | 22.5 °C | 116.08 mm |
| June | 15.4 °C | 28 °C | 120.14 mm |
| July | 17.5 °C | 29.8 °C | 100.84 mm |
| August | 15.9 °C | 28.6 °C | 106.68 mm |
| September | 10.8 °C | 25.2 °C | 76.96 mm |
| October | 3.7 °C | 18.1 °C | 57.91 mm |
| November | -3.4 °C | 9 °C | 34.8 mm |
| December | -9.1 °C | 1.4 °C | 27.69 mm |
| Annual | 3.2 °C | 15.7 °C | 810.52 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |