Harper, Kansas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.8 °C (low) to 20.8 °C (high). Annual precipitation averages 832.4 Millimeters. Harper is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5 °C | 7.2 °C | 22.61 mm |
| February | -3.3 °C | 9.6 °C | 31.5 mm |
| March | 1.7 °C | 15.1 °C | 59.44 mm |
| April | 6.6 °C | 20.3 °C | 74.68 mm |
| May | 12.9 °C | 25.6 °C | 121.16 mm |
| June | 18.4 °C | 31.3 °C | 119.89 mm |
| July | 20.9 °C | 33.9 °C | 98.55 mm |
| August | 20.1 °C | 33 °C | 90.68 mm |
| September | 15.4 °C | 28.8 °C | 68.07 mm |
| October | 8.3 °C | 22 °C | 76.2 mm |
| November | 1.5 °C | 14.4 °C | 36.32 mm |
| December | -3.7 °C | 7.9 °C | 33.27 mm |
| Annual | 7.8 °C | 20.8 °C | 832.37 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |