Mount Union, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.3 °F (low) to 61 °F (high). Annual precipitation averages 38 Inches. Mount Union 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.3 °F | 31.7 °F | 1.46 in. |
| February | 19.1 °F | 36.5 °F | 1.75 in. |
| March | 29.2 °F | 49.2 °F | 2.44 in. |
| April | 40.2 °F | 62.3 °F | 3.72 in. |
| May | 52.1 °F | 72.8 °F | 5.1 in. |
| June | 61.9 °F | 82.0 °F | 4.9 in. |
| July | 65.2 °F | 85.3 °F | 4.06 in. |
| August | 63.0 °F | 83.8 °F | 3.96 in. |
| September | 54.1 °F | 77.6 °F | 3.6 in. |
| October | 42.6 °F | 64.8 °F | 2.88 in. |
| November | 31.2 °F | 49.5 °F | 2.28 in. |
| December | 21.2 °F | 37.0 °F | 1.8 in. |
| Annual | 41.3 °F | 61 °F | 37.95 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |