Marthasville, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.1 °C (low) to 18.9 °C (high). Annual precipitation averages 1120.6 Millimeters. Marthasville is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.8 °C | 4.3 °C | 64.01 mm |
| February | -3.9 °C | 7.4 °C | 60.96 mm |
| March | 0.9 °C | 13.2 °C | 90.42 mm |
| April | 6.7 °C | 19.7 °C | 119.13 mm |
| May | 12.6 °C | 24.4 °C | 134.87 mm |
| June | 17.6 °C | 28.9 °C | 114.55 mm |
| July | 19.8 °C | 31.1 °C | 104.9 mm |
| August | 18.5 °C | 30.5 °C | 96.77 mm |
| September | 13.9 °C | 26.9 °C | 93.47 mm |
| October | 7.1 °C | 20.6 °C | 85.34 mm |
| November | 1.3 °C | 13.1 °C | 87.88 mm |
| December | -3.4 °C | 6.8 °C | 68.33 mm |
| Annual | 7.1 °C | 18.9 °C | 1120.63 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |