Port Henry, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.4 °C (low) to 13.5 °C (high). Annual precipitation averages 962.2 Millimeters. Port Henry is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.7 °C | -1.6 °C | 63.5 mm |
| February | -11.2 °C | -0.4 °C | 52.58 mm |
| March | -5.7 °C | 4.5 °C | 73.15 mm |
| April | 0.8 °C | 12.9 °C | 78.74 mm |
| May | 7.4 °C | 20 °C | 78.74 mm |
| June | 12.8 °C | 24.9 °C | 105.92 mm |
| July | 15.6 °C | 27.8 °C | 102.36 mm |
| August | 14.7 °C | 26.8 °C | 91.44 mm |
| September | 10.2 °C | 22.7 °C | 81.03 mm |
| October | 3.9 °C | 14.9 °C | 91.44 mm |
| November | -1.2 °C | 7.8 °C | 69.09 mm |
| December | -7.2 °C | 1.4 °C | 74.17 mm |
| Annual | 2.4 °C | 13.5 °C | 962.16 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |