Keithsburg, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.8 °F (low) to 61 °F (high). Annual precipitation averages 36.8 Inches. Keithsburg 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.5 °F | 31.7 °F | 1.49 in. |
| February | 18.9 °F | 36.0 °F | 1.76 in. |
| March | 29.8 °F | 48.7 °F | 2.47 in. |
| April | 40.8 °F | 62.0 °F | 3.59 in. |
| May | 52.5 °F | 72.7 °F | 4.71 in. |
| June | 62.3 °F | 82.3 °F | 4.74 in. |
| July | 65.8 °F | 85.8 °F | 3.77 in. |
| August | 63.5 °F | 83.9 °F | 3.92 in. |
| September | 55.3 °F | 77.5 °F | 3.47 in. |
| October | 43.5 °F | 64.5 °F | 2.77 in. |
| November | 31.9 °F | 49.9 °F | 2.21 in. |
| December | 21.5 °F | 36.8 °F | 1.87 in. |
| Annual | 41.8 °F | 61 °F | 36.77 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |