Fort Madison, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.1 °C (low) to 16.6 °C (high). Annual precipitation averages 1002.5 Millimeters. Fort Madison 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.3 °C | 0.7 °C | 43.94 mm |
| February | -6.4 °C | 3.2 °C | 48.51 mm |
| March | -0.6 °C | 10.1 °C | 66.8 mm |
| April | 5.5 °C | 17.1 °C | 97.03 mm |
| May | 11.9 °C | 22.8 °C | 131.83 mm |
| June | 17.3 °C | 27.9 °C | 127.76 mm |
| July | 19.4 °C | 29.9 °C | 105.41 mm |
| August | 18.2 °C | 29.1 °C | 96.77 mm |
| September | 13.5 °C | 25.6 °C | 93.47 mm |
| October | 7 °C | 18.6 °C | 77.22 mm |
| November | 0.5 °C | 10.3 °C | 64.26 mm |
| December | -5.2 °C | 3.4 °C | 49.53 mm |
| Annual | 6.1 °C | 16.6 °C | 1002.53 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |