West Mifflin, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.7 °C (low) to 16.5 °C (high). Annual precipitation averages 1048 Millimeters. West Mifflin 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 | -5.9 °C | 2.9 °C | 80.52 mm |
| February | -5.3 °C | 4.4 °C | 62.74 mm |
| March | -1.3 °C | 9.6 °C | 85.09 mm |
| April | 4.4 °C | 16.9 °C | 86.61 mm |
| May | 10.3 °C | 22.3 °C | 97.28 mm |
| June | 15.1 °C | 26.7 °C | 113.79 mm |
| July | 17.4 °C | 28.8 °C | 107.7 mm |
| August | 16.6 °C | 28.1 °C | 93.22 mm |
| September | 12.7 °C | 24.5 °C | 88.14 mm |
| October | 6.4 °C | 17.8 °C | 79.25 mm |
| November | 1.1 °C | 11.1 °C | 74.93 mm |
| December | -2.9 °C | 5.3 °C | 78.74 mm |
| Annual | 5.7 °C | 16.5 °C | 1048.01 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |