West Union, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.5 °C (low) to 11.3 °C (high). Annual precipitation averages 688.1 Millimeters. West Union is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.7 °C | -6.8 °C | 16 mm |
| February | -14.7 °C | -3.9 °C | 14.99 mm |
| March | -7.7 °C | 2.8 °C | 31.75 mm |
| April | 0.1 °C | 11.7 °C | 58.17 mm |
| May | 7.4 °C | 19.1 °C | 82.04 mm |
| June | 13.4 °C | 24.6 °C | 111 mm |
| July | 15.9 °C | 27.2 °C | 100.33 mm |
| August | 14.3 °C | 25.9 °C | 87.12 mm |
| September | 9.5 °C | 21.6 °C | 71.37 mm |
| October | 2.1 °C | 13 °C | 66.04 mm |
| November | -5.2 °C | 3.7 °C | 28.7 mm |
| December | -12.3 °C | -3.8 °C | 20.57 mm |
| Annual | 0.5 °C | 11.3 °C | 688.08 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |