Grampian, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3 °C (low) to 14.3 °C (high). Annual precipitation averages 1241.8 Millimeters. Grampian is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.7 °C | 0.2 °C | 96.77 mm |
| February | -8.1 °C | 1.9 °C | 79.5 mm |
| March | -4.2 °C | 6.9 °C | 94.23 mm |
| April | 1.7 °C | 14.7 °C | 107.19 mm |
| May | 7.7 °C | 20.6 °C | 108.46 mm |
| June | 12.2 °C | 24.6 °C | 136.14 mm |
| July | 14.6 °C | 26.8 °C | 112.27 mm |
| August | 13.8 °C | 26 °C | 109.22 mm |
| September | 9.9 °C | 22.3 °C | 107.7 mm |
| October | 3.9 °C | 15.7 °C | 105.66 mm |
| November | -1.3 °C | 8.7 °C | 88.9 mm |
| December | -5.4 °C | 2.6 °C | 95.76 mm |
| Annual | 3 °C | 14.3 °C | 1241.8 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |