Glen Lyon, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.2 °C (low) to 15.9 °C (high). Annual precipitation averages 1172.7 Millimeters. Glen Lyon 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.7 °C | 1.8 °C | 82.04 mm |
| February | -7 °C | 3.3 °C | 62.23 mm |
| March | -2.8 °C | 8.1 °C | 88.65 mm |
| April | 2.9 °C | 15.8 °C | 96.77 mm |
| May | 8.6 °C | 22 °C | 104.65 mm |
| June | 13.6 °C | 26.4 °C | 117.09 mm |
| July | 16 °C | 29.1 °C | 114.05 mm |
| August | 15.2 °C | 27.9 °C | 116.08 mm |
| September | 11.2 °C | 24.2 °C | 117.35 mm |
| October | 4.9 °C | 17.3 °C | 105.16 mm |
| November | 0.1 °C | 10.6 °C | 80.01 mm |
| December | -4.2 °C | 4.6 °C | 88.65 mm |
| Annual | 4.2 °C | 15.9 °C | 1172.73 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 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 | Dfb - Humid Continental Mild Summer, Wet All Year |