Galena, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.9 °F (low) to 58.1 °F (high). Annual precipitation averages 38.9 Inches. 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 | 11.2 °F | 28.2 °F | 1.31 in. |
| February | 14.6 °F | 32.6 °F | 1.55 in. |
| March | 25.8 °F | 45.4 °F | 2.14 in. |
| April | 36.7 °F | 58.8 °F | 3.94 in. |
| May | 48.2 °F | 70.6 °F | 4.33 in. |
| June | 58.5 °F | 80.2 °F | 5.9 in. |
| July | 62.2 °F | 83.3 °F | 4.64 in. |
| August | 60.1 °F | 81.5 °F | 4.08 in. |
| September | 51.6 °F | 74.8 °F | 3.8 in. |
| October | 39.9 °F | 61.8 °F | 3.06 in. |
| November | 28.3 °F | 46.3 °F | 2.31 in. |
| December | 17.6 °F | 33.7 °F | 1.8 in. |
| Annual | 37.9 °F | 58.1 °F | 38.86 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |