Castalia, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.5 °F (low) to 59.1 °F (high). Annual precipitation averages 38.9 Inches. Castalia is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 19.4 °F | 33.2 °F | 2.61 in. |
| February | 20.9 °F | 36.0 °F | 2.18 in. |
| March | 28.6 °F | 45.1 °F | 2.77 in. |
| April | 39.4 °F | 57.8 °F | 3.92 in. |
| May | 51.1 °F | 69.3 °F | 3.78 in. |
| June | 61.2 °F | 78.6 °F | 4.08 in. |
| July | 64.8 °F | 82.6 °F | 3.86 in. |
| August | 63.4 °F | 80.8 °F | 3.48 in. |
| September | 56.3 °F | 74.9 °F | 3.45 in. |
| October | 44.9 °F | 63.2 °F | 3.14 in. |
| November | 34.5 °F | 49.5 °F | 2.85 in. |
| December | 25.6 °F | 38.2 °F | 2.79 in. |
| Annual | 42.5 °F | 59.1 °F | 38.91 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |