Afton, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.2 °C (low) to 15.7 °C (high). Annual precipitation averages 927.1 Millimeters. Afton 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 | -10.6 °C | -0.4 °C | 23.11 mm |
| February | -8.3 °C | 2.4 °C | 32.77 mm |
| March | -2.5 °C | 9.4 °C | 53.34 mm |
| April | 3.6 °C | 16.3 °C | 93.47 mm |
| May | 10.2 °C | 21.8 °C | 135.64 mm |
| June | 15.8 °C | 27 °C | 127 mm |
| July | 18.1 °C | 29.3 °C | 106.93 mm |
| August | 16.8 °C | 28.6 °C | 104.39 mm |
| September | 11.7 °C | 24.5 °C | 95.25 mm |
| October | 4.9 °C | 17.7 °C | 68.83 mm |
| November | -1.7 °C | 9.3 °C | 51.31 mm |
| December | -7.6 °C | 2.3 °C | 35.05 mm |
| Annual | 4.2 °C | 15.7 °C | 927.09 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |