Allen, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 34.5 °F (low) to 60.6 °F (high). Annual precipitation averages 20.1 Inches. 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 | 13.2 °F | 35.6 °F | 0.39 in. |
| February | 15.2 °F | 38.5 °F | 0.56 in. |
| March | 23.4 °F | 49.4 °F | 1.11 in. |
| April | 31.8 °F | 58.4 °F | 2.29 in. |
| May | 42.2 °F | 68.2 °F | 3.42 in. |
| June | 52.8 °F | 79.3 °F | 3.51 in. |
| July | 59.0 °F | 87.3 °F | 2.51 in. |
| August | 57.0 °F | 86.2 °F | 2.01 in. |
| September | 47.2 °F | 77.5 °F | 1.47 in. |
| October | 34.2 °F | 61.9 °F | 1.63 in. |
| November | 22.8 °F | 47.9 °F | 0.64 in. |
| December | 14.6 °F | 36.8 °F | 0.53 in. |
| Annual | 34.5 °F | 60.6 °F | 20.07 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |