Marshall, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.3 °C (low) to 17.9 °C (high). Annual precipitation averages 1126.2 Millimeters. Marshall is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.5 °C | 2.7 °C | 72.9 mm |
| February | -4.9 °C | 5.4 °C | 63.25 mm |
| March | 0.2 °C | 11.4 °C | 86.61 mm |
| April | 6 °C | 18.7 °C | 134.87 mm |
| May | 11.9 °C | 23.8 °C | 121.92 mm |
| June | 16.7 °C | 28.7 °C | 119.89 mm |
| July | 18.3 °C | 30.4 °C | 110.49 mm |
| August | 17.1 °C | 29.8 °C | 75.18 mm |
| September | 12.8 °C | 26.8 °C | 80.77 mm |
| October | 6.4 °C | 20.1 °C | 93.98 mm |
| November | 0.9 °C | 11.8 °C | 94.23 mm |
| December | -3.7 °C | 5.2 °C | 72.14 mm |
| Annual | 6.3 °C | 17.9 °C | 1126.23 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |