Armagh, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.3 °C (low) to 15.2 °C (high). Annual precipitation averages 1244.1 Millimeters. Armagh is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.3 °C | 1.6 °C | 100.84 mm |
| February | -6.5 °C | 3.3 °C | 80.77 mm |
| March | -2.8 °C | 8.2 °C | 101.6 mm |
| April | 3.1 °C | 15.8 °C | 106.68 mm |
| May | 8.8 °C | 21.3 °C | 110.49 mm |
| June | 13.5 °C | 25.2 °C | 120.14 mm |
| July | 15.7 °C | 27.2 °C | 124.21 mm |
| August | 14.9 °C | 26.6 °C | 112.27 mm |
| September | 11.3 °C | 23 °C | 103.89 mm |
| October | 5.2 °C | 16.6 °C | 89.92 mm |
| November | -0.3 °C | 9.9 °C | 94.74 mm |
| December | -4.2 °C | 4 °C | 98.55 mm |
| Annual | 4.3 °C | 15.2 °C | 1244.1 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |