Mercer, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40 °F (low) to 60.9 °F (high). Annual precipitation averages 38.5 Inches. 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 | 14.0 °F | 32.4 °F | 1.01 in. |
| February | 17.9 °F | 37.7 °F | 1.31 in. |
| March | 28.4 °F | 50.1 °F | 2.2 in. |
| April | 39.1 °F | 61.8 °F | 4.03 in. |
| May | 50.5 °F | 71.5 °F | 5.51 in. |
| June | 60.4 °F | 80.8 °F | 5.05 in. |
| July | 64.6 °F | 85.1 °F | 4.62 in. |
| August | 62.1 °F | 83.6 °F | 4.49 in. |
| September | 53.3 °F | 76.5 °F | 3.77 in. |
| October | 41.2 °F | 64.3 °F | 3.1 in. |
| November | 29.4 °F | 49.7 °F | 1.92 in. |
| December | 19.3 °F | 37.4 °F | 1.51 in. |
| Annual | 40 °F | 60.9 °F | 38.52 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 5b : -15°F to -10°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 |