Union Star, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.5 °C (low) to 17.4 °C (high). Annual precipitation averages 984.5 Millimeters. Union Star is located in USDA Plant Hardiness Zone 6a. 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 | -8.8 °C | 1.8 °C | 24.13 mm |
| February | -6.5 °C | 4.7 °C | 33.53 mm |
| March | -0.8 °C | 11.6 °C | 60.45 mm |
| April | 4.8 °C | 17.7 °C | 95 mm |
| May | 11.3 °C | 23.3 °C | 138.68 mm |
| June | 16.8 °C | 28.4 °C | 136.91 mm |
| July | 19.1 °C | 30.7 °C | 123.7 mm |
| August | 17.8 °C | 29.9 °C | 104.9 mm |
| September | 12.8 °C | 25.9 °C | 99.06 mm |
| October | 6.1 °C | 19.1 °C | 79.76 mm |
| November | -0.3 °C | 11.3 °C | 49.53 mm |
| December | -5.9 °C | 4.2 °C | 38.86 mm |
| Annual | 5.5 °C | 17.4 °C | 984.51 mm |
| 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |