Smithfield, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.6 °C (low) to 17.1 °C (high). Annual precipitation averages 1136.2 Millimeters. Smithfield is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.7 °C | 3.7 °C | 84.84 mm |
| February | -4.8 °C | 5.4 °C | 73.41 mm |
| March | -1.2 °C | 10.5 °C | 92.71 mm |
| April | 4.3 °C | 17.8 °C | 97.79 mm |
| May | 9.9 °C | 22.9 °C | 112.52 mm |
| June | 14.7 °C | 27 °C | 114.3 mm |
| July | 17.1 °C | 28.9 °C | 119.89 mm |
| August | 16.3 °C | 28.4 °C | 98.3 mm |
| September | 12.4 °C | 25 °C | 92.2 mm |
| October | 6.1 °C | 18.2 °C | 81.03 mm |
| November | 0.7 °C | 11.6 °C | 82.8 mm |
| December | -2.9 °C | 5.9 °C | 86.36 mm |
| Annual | 5.6 °C | 17.1 °C | 1136.15 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 |