Mercer, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.5 °C (low) to 16.1 °C (high). Annual precipitation averages 978.4 Millimeters. Mercer 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 | -10 °C | 0.2 °C | 25.65 mm |
| February | -7.8 °C | 3.2 °C | 33.27 mm |
| March | -2 °C | 10.1 °C | 55.88 mm |
| April | 3.9 °C | 16.6 °C | 102.36 mm |
| May | 10.3 °C | 21.9 °C | 139.95 mm |
| June | 15.8 °C | 27.1 °C | 128.27 mm |
| July | 18.1 °C | 29.5 °C | 117.35 mm |
| August | 16.7 °C | 28.7 °C | 114.05 mm |
| September | 11.8 °C | 24.7 °C | 95.76 mm |
| October | 5.1 °C | 17.9 °C | 78.74 mm |
| November | -1.4 °C | 9.8 °C | 48.77 mm |
| December | -7.1 °C | 3 °C | 38.35 mm |
| Annual | 4.5 °C | 16.1 °C | 978.4 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 5b : -26.1°C to -23.3°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 |