Jefferson, Ohio has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.2 °C (low) to 14.7 °C (high). Annual precipitation averages 1098.3 Millimeters. Jefferson is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.7 °C | 0.7 °C | 82.3 mm |
| February | -7.7 °C | 2 °C | 58.42 mm |
| March | -3.4 °C | 6.8 °C | 74.93 mm |
| April | 2.4 °C | 14.3 °C | 99.82 mm |
| May | 8.4 °C | 20.6 °C | 89.92 mm |
| June | 13.4 °C | 25.2 °C | 101.6 mm |
| July | 15.7 °C | 27.3 °C | 108.46 mm |
| August | 14.8 °C | 26.4 °C | 90.68 mm |
| September | 11.3 °C | 23.1 °C | 103.38 mm |
| October | 5.7 °C | 16.4 °C | 107.19 mm |
| November | 0.8 °C | 9.6 °C | 91.44 mm |
| December | -3.8 °C | 3.6 °C | 90.17 mm |
| Annual | 4.2 °C | 14.7 °C | 1098.31 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |