Harvel, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.4 °C (low) to 17.6 °C (high). Annual precipitation averages 1011.4 Millimeters. Harvel is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.8 °C | 2 °C | 60.2 mm |
| February | -4.8 °C | 4.9 °C | 51.31 mm |
| March | 0.2 °C | 11.2 °C | 71.63 mm |
| April | 5.9 °C | 18.2 °C | 109.98 mm |
| May | 12.2 °C | 23.8 °C | 120.9 mm |
| June | 17.2 °C | 28.6 °C | 111.25 mm |
| July | 18.8 °C | 30.2 °C | 94.74 mm |
| August | 17.6 °C | 29.6 °C | 82.8 mm |
| September | 13 °C | 26.7 °C | 82.3 mm |
| October | 6.7 °C | 19.8 °C | 83.31 mm |
| November | 1 °C | 11.4 °C | 83.06 mm |
| December | -3.9 °C | 4.8 °C | 59.94 mm |
| Annual | 6.4 °C | 17.6 °C | 1011.42 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |