Jefferson, Ohio has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 39.5 °F (low) to 58.4 °F (high). Annual precipitation averages 43.2 Inches. 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 | 18.2 °F | 33.3 °F | 3.24 in. |
| February | 18.2 °F | 35.6 °F | 2.3 in. |
| March | 25.8 °F | 44.3 °F | 2.95 in. |
| April | 36.4 °F | 57.7 °F | 3.93 in. |
| May | 47.2 °F | 69.1 °F | 3.54 in. |
| June | 56.2 °F | 77.4 °F | 4.0 in. |
| July | 60.3 °F | 81.2 °F | 4.27 in. |
| August | 58.7 °F | 79.6 °F | 3.57 in. |
| September | 52.3 °F | 73.6 °F | 4.07 in. |
| October | 42.3 °F | 61.5 °F | 4.22 in. |
| November | 33.4 °F | 49.3 °F | 3.6 in. |
| December | 25.1 °F | 38.4 °F | 3.55 in. |
| Annual | 39.5 °F | 58.4 °F | 43.24 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |