Jefferson, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34 °F (low) to 54.8 °F (high). Annual precipitation averages 45.4 Inches. Jefferson is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 11.4 °F | 29.6 °F | 2.99 in. |
| February | 12.8 °F | 31.6 °F | 2.44 in. |
| March | 19.9 °F | 39.9 °F | 3.52 in. |
| April | 30.8 °F | 54.1 °F | 3.67 in. |
| May | 41.3 °F | 66.4 °F | 3.89 in. |
| June | 50.8 °F | 73.9 °F | 4.62 in. |
| July | 55.1 °F | 77.7 °F | 4.51 in. |
| August | 53.9 °F | 76.8 °F | 4.36 in. |
| September | 47.1 °F | 70.3 °F | 4.18 in. |
| October | 36.8 °F | 58.3 °F | 4.5 in. |
| November | 27.8 °F | 44.6 °F | 3.3 in. |
| December | 19.7 °F | 34.7 °F | 3.37 in. |
| Annual | 34 °F | 54.8 °F | 45.35 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |