Belfast, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.1 °F (low) to 57.4 °F (high). Annual precipitation averages 39.4 Inches. Belfast is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.4 °F | 31.8 °F | 2.65 in. |
| February | 14.3 °F | 34.3 °F | 2.04 in. |
| March | 21.0 °F | 42.7 °F | 2.64 in. |
| April | 31.6 °F | 56.6 °F | 3.34 in. |
| May | 42.3 °F | 68.8 °F | 3.42 in. |
| June | 51.5 °F | 76.8 °F | 3.9 in. |
| July | 55.8 °F | 80.7 °F | 4.02 in. |
| August | 54.5 °F | 79.3 °F | 3.82 in. |
| September | 47.9 °F | 73.0 °F | 3.76 in. |
| October | 37.6 °F | 60.3 °F | 3.74 in. |
| November | 28.9 °F | 47.4 °F | 2.99 in. |
| December | 21.0 °F | 36.8 °F | 3.04 in. |
| Annual | 35.1 °F | 57.4 °F | 39.36 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |