Johnstown, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.8 °C (low) to 13.4 °C (high). Annual precipitation averages 1172.5 Millimeters. Johnstown 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.7 °C | -1.3 °C | 83.57 mm |
| February | -9.8 °C | 0.2 °C | 74.93 mm |
| March | -5.4 °C | 4.8 °C | 88.39 mm |
| April | 1.3 °C | 12.7 °C | 99.31 mm |
| May | 7.8 °C | 20 °C | 99.57 mm |
| June | 12.9 °C | 24.6 °C | 118.11 mm |
| July | 15.7 °C | 27 °C | 114.55 mm |
| August | 14.7 °C | 26.2 °C | 114.3 mm |
| September | 10.6 °C | 22.2 °C | 94.74 mm |
| October | 4.2 °C | 15.2 °C | 110.24 mm |
| November | -1.3 °C | 7.7 °C | 84.07 mm |
| December | -6.4 °C | 1.5 °C | 90.68 mm |
| Annual | 2.8 °C | 13.4 °C | 1172.46 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 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 |