Napoleon, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.8 °C (low) to 18 °C (high). Annual precipitation averages 1070.9 Millimeters. Napoleon is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.9 °C | 2.9 °C | 35.56 mm |
| February | -5.7 °C | 6 °C | 45.72 mm |
| March | -0.4 °C | 12.2 °C | 65.28 mm |
| April | 5.2 °C | 18.3 °C | 104.9 mm |
| May | 11.3 °C | 23.6 °C | 143 mm |
| June | 16.9 °C | 28.5 °C | 138.18 mm |
| July | 19.1 °C | 30.8 °C | 123.7 mm |
| August | 17.7 °C | 30.3 °C | 111.51 mm |
| September | 12.7 °C | 26.1 °C | 111.76 mm |
| October | 6.1 °C | 19.7 °C | 88.39 mm |
| November | -0.2 °C | 11.7 °C | 60.2 mm |
| December | -5.4 °C | 5.3 °C | 42.67 mm |
| Annual | 5.8 °C | 18 °C | 1070.87 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |