Unionville, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.2 °F (low) to 60.6 °F (high). Annual precipitation averages 38.6 Inches. Unionville is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.7 °F | 31.7 °F | 1.2 in. |
| February | 17.6 °F | 36.4 °F | 1.54 in. |
| March | 28.3 °F | 49.4 °F | 2.24 in. |
| April | 39.3 °F | 61.8 °F | 3.91 in. |
| May | 51.0 °F | 71.5 °F | 5.37 in. |
| June | 60.9 °F | 81.0 °F | 5.36 in. |
| July | 64.8 °F | 85.0 °F | 4.44 in. |
| August | 62.5 °F | 83.6 °F | 4.16 in. |
| September | 53.7 °F | 76.6 °F | 3.81 in. |
| October | 41.8 °F | 64.1 °F | 2.9 in. |
| November | 29.5 °F | 49.2 °F | 2.15 in. |
| December | 19.7 °F | 36.8 °F | 1.53 in. |
| Annual | 40.2 °F | 60.6 °F | 38.61 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |