La Harpe, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 16.5 °C (high). Annual precipitation averages 972.3 Millimeters. La Harpe is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.1 °C | 0.4 °C | 42.16 mm |
| February | -7 °C | 3 °C | 47.75 mm |
| March | -1.3 °C | 10.1 °C | 59.69 mm |
| April | 4.7 °C | 17.2 °C | 96.77 mm |
| May | 11.3 °C | 22.9 °C | 132.08 mm |
| June | 16.7 °C | 27.9 °C | 120.14 mm |
| July | 18.6 °C | 29.8 °C | 101.09 mm |
| August | 17.3 °C | 28.9 °C | 86.61 mm |
| September | 12.7 °C | 25.6 °C | 92.96 mm |
| October | 6.1 °C | 18.6 °C | 77.22 mm |
| November | -0.3 °C | 10.2 °C | 66.29 mm |
| December | -5.8 °C | 3.3 °C | 49.53 mm |
| Annual | 5.3 °C | 16.5 °C | 972.29 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |