Marseilles, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.8 °C (low) to 15.6 °C (high). Annual precipitation averages 974.9 Millimeters. Marseilles is located in USDA Plant Hardiness Zone 5b. 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 | 50.29 mm |
| February | -7.3 °C | 1.9 °C | 46.74 mm |
| March | -2 °C | 8.7 °C | 63.5 mm |
| April | 3.9 °C | 16.1 °C | 89.66 mm |
| May | 10.3 °C | 22.3 °C | 117.35 mm |
| June | 15.7 °C | 27.2 °C | 119.38 mm |
| July | 17.7 °C | 28.8 °C | 99.57 mm |
| August | 16.6 °C | 27.8 °C | 100.08 mm |
| September | 12.2 °C | 25 °C | 87.63 mm |
| October | 5.7 °C | 17.8 °C | 79.76 mm |
| November | -0.4 °C | 9.6 °C | 67.56 mm |
| December | -6 °C | 2.4 °C | 53.34 mm |
| Annual | 4.8 °C | 15.6 °C | 974.86 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 5b : -26.1°C to -23.3°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 |