Galena, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.3 °C (low) to 14.5 °C (high). Annual precipitation averages 987 Millimeters. Galena is located in USDA Plant Hardiness Zone 5a. 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 | -11.6 °C | -2.1 °C | 33.27 mm |
| February | -9.7 °C | 0.3 °C | 39.37 mm |
| March | -3.4 °C | 7.4 °C | 54.36 mm |
| April | 2.6 °C | 14.9 °C | 100.08 mm |
| May | 9 °C | 21.4 °C | 109.98 mm |
| June | 14.7 °C | 26.8 °C | 149.86 mm |
| July | 16.8 °C | 28.5 °C | 117.86 mm |
| August | 15.6 °C | 27.5 °C | 103.63 mm |
| September | 10.9 °C | 23.8 °C | 96.52 mm |
| October | 4.4 °C | 16.6 °C | 77.72 mm |
| November | -2.1 °C | 7.9 °C | 58.67 mm |
| December | -8 °C | 0.9 °C | 45.72 mm |
| Annual | 3.3 °C | 14.5 °C | 987.04 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |