Castana, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.7 °F (low) to 60.3 °F (high). Annual precipitation averages 31.9 Inches. 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 | 10.6 °F | 29.9 °F | 0.68 in. |
| February | 14.7 °F | 35.0 °F | 0.84 in. |
| March | 25.8 °F | 48.2 °F | 1.61 in. |
| April | 36.6 °F | 61.7 °F | 3.54 in. |
| May | 49.0 °F | 72.5 °F | 4.57 in. |
| June | 59.8 °F | 82.4 °F | 4.73 in. |
| July | 63.5 °F | 85.7 °F | 3.97 in. |
| August | 60.7 °F | 83.4 °F | 4.2 in. |
| September | 51.5 °F | 77.4 °F | 3.03 in. |
| October | 38.7 °F | 64.5 °F | 2.28 in. |
| November | 25.8 °F | 48.2 °F | 1.37 in. |
| December | 15.6 °F | 34.5 °F | 1.09 in. |
| Annual | 37.7 °F | 60.3 °F | 31.91 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |