Perth, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.1 °C (low) to 13 °C (high). Annual precipitation averages 1198.4 Millimeters. Perth is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.2 °C | -1.7 °C | 93.47 mm |
| February | -10.5 °C | -0.1 °C | 71.88 mm |
| March | -6 °C | 4.7 °C | 89.41 mm |
| April | 0.7 °C | 12.5 °C | 96.27 mm |
| May | 7.1 °C | 19.4 °C | 107.44 mm |
| June | 12.1 °C | 23.9 °C | 119.38 mm |
| July | 15.1 °C | 26.4 °C | 113.79 mm |
| August | 13.9 °C | 25.6 °C | 103.12 mm |
| September | 9.9 °C | 21.6 °C | 107.95 mm |
| October | 3.6 °C | 14.8 °C | 111.25 mm |
| November | -2 °C | 7.4 °C | 88.39 mm |
| December | -7.2 °C | 1.2 °C | 96.01 mm |
| Annual | 2.1 °C | 13 °C | 1198.36 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°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 |