Afton, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.6 °C (low) to 12.9 °C (high). Annual precipitation averages 870.7 Millimeters. Afton is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.8 °C | -4.5 °C | 24.38 mm |
| February | -11.9 °C | -1.8 °C | 21.84 mm |
| March | -5.2 °C | 5.1 °C | 42.16 mm |
| April | 2.1 °C | 13.3 °C | 76.96 mm |
| May | 9.1 °C | 20.2 °C | 108.71 mm |
| June | 14.8 °C | 25.8 °C | 134.87 mm |
| July | 17.4 °C | 28.2 °C | 113.54 mm |
| August | 15.9 °C | 26.9 °C | 114.55 mm |
| September | 11.3 °C | 22.7 °C | 87.88 mm |
| October | 4.2 °C | 14.8 °C | 71.88 mm |
| November | -2.9 °C | 5.9 °C | 40.89 mm |
| December | -9.8 °C | -1.6 °C | 33.02 mm |
| Annual | 2.6 °C | 12.9 °C | 870.68 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |