Galesburg, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 15.7 °C (high). Annual precipitation averages 989.8 Millimeters. Galesburg is located in USDA Plant Hardiness Zone 5b. 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 | -9.8 °C | -0.6 °C | 44.7 mm |
| February | -7.9 °C | 1.9 °C | 49.28 mm |
| March | -2.1 °C | 9.2 °C | 62.23 mm |
| April | 3.8 °C | 16.4 °C | 98.04 mm |
| May | 10.6 °C | 22.4 °C | 132.08 mm |
| June | 16 °C | 27.3 °C | 120.14 mm |
| July | 17.8 °C | 29 °C | 102.11 mm |
| August | 16.6 °C | 28.1 °C | 94.23 mm |
| September | 12 °C | 24.8 °C | 98.81 mm |
| October | 5.4 °C | 17.8 °C | 73.41 mm |
| November | -0.9 °C | 9.4 °C | 63.25 mm |
| December | -6.4 °C | 2.4 °C | 51.56 mm |
| Annual | 4.6 °C | 15.7 °C | 989.84 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |