Thornburg, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.1 °C (low) to 16.7 °C (high). Annual precipitation averages 1034.6 Millimeters. Thornburg is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.6 °C | 3.1 °C | 81.53 mm |
| February | -4.8 °C | 4.5 °C | 65.28 mm |
| March | -0.9 °C | 9.6 °C | 81.28 mm |
| April | 4.7 °C | 17.1 °C | 87.63 mm |
| May | 10.4 °C | 22.4 °C | 98.81 mm |
| June | 15.3 °C | 27 °C | 105.66 mm |
| July | 17.7 °C | 29.2 °C | 107.7 mm |
| August | 17 °C | 28.4 °C | 86.36 mm |
| September | 13.2 °C | 24.8 °C | 89.66 mm |
| October | 6.8 °C | 18 °C | 75.95 mm |
| November | 1.4 °C | 11.2 °C | 74.17 mm |
| December | -2.6 °C | 5.5 °C | 80.52 mm |
| Annual | 6.1 °C | 16.7 °C | 1034.55 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |