Union Star, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.9 °F (low) to 63.3 °F (high). Annual precipitation averages 38.8 Inches. 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 | 16.1 °F | 35.2 °F | 0.95 in. |
| February | 20.3 °F | 40.5 °F | 1.32 in. |
| March | 30.5 °F | 52.9 °F | 2.38 in. |
| April | 40.7 °F | 63.8 °F | 3.74 in. |
| May | 52.4 °F | 73.9 °F | 5.46 in. |
| June | 62.2 °F | 83.1 °F | 5.39 in. |
| July | 66.3 °F | 87.2 °F | 4.87 in. |
| August | 64.1 °F | 85.8 °F | 4.13 in. |
| September | 55.1 °F | 78.7 °F | 3.9 in. |
| October | 42.9 °F | 66.4 °F | 3.14 in. |
| November | 31.4 °F | 52.4 °F | 1.95 in. |
| December | 21.3 °F | 39.5 °F | 1.53 in. |
| Annual | 41.9 °F | 63.3 °F | 38.76 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 6a : -10°F to -5°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 |