Allen, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1.4 °C (low) to 15.9 °C (high). Annual precipitation averages 509.8 Millimeters. Allen is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.4 °C | 2 °C | 9.91 mm |
| February | -9.3 °C | 3.6 °C | 14.22 mm |
| March | -4.8 °C | 9.7 °C | 28.19 mm |
| April | -0.1 °C | 14.7 °C | 58.17 mm |
| May | 5.7 °C | 20.1 °C | 86.87 mm |
| June | 11.6 °C | 26.3 °C | 89.15 mm |
| July | 15 °C | 30.7 °C | 63.75 mm |
| August | 13.9 °C | 30.1 °C | 51.05 mm |
| September | 8.4 °C | 25.3 °C | 37.34 mm |
| October | 1.2 °C | 16.6 °C | 41.4 mm |
| November | -5.1 °C | 8.8 °C | 16.26 mm |
| December | -9.7 °C | 2.7 °C | 13.46 mm |
| Annual | 1.4 °C | 15.9 °C | 509.77 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| 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 | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |