Sullivan, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 38 °F (low) to 57 °F (high). Annual precipitation averages 44.4 Inches. Sullivan is located in USDA Plant Hardiness Zone 5b. 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 | 14.6 °F | 30.8 °F | 3.05 in. |
| February | 15.4 °F | 33.0 °F | 2.69 in. |
| March | 23.2 °F | 40.9 °F | 3.13 in. |
| April | 34.8 °F | 55.6 °F | 3.73 in. |
| May | 46.3 °F | 68.7 °F | 3.78 in. |
| June | 55.6 °F | 76.7 °F | 4.18 in. |
| July | 60.4 °F | 81.3 °F | 4.01 in. |
| August | 58.8 °F | 80.0 °F | 4.15 in. |
| September | 51.5 °F | 73.1 °F | 3.93 in. |
| October | 41.4 °F | 59.9 °F | 4.57 in. |
| November | 32.0 °F | 47.6 °F | 3.5 in. |
| December | 22.5 °F | 36.3 °F | 3.63 in. |
| Annual | 38 °F | 57 °F | 44.35 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 5b : -15°F to -10°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 |