Mifflintown, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.3 °C (low) to 16.9 °C (high). Annual precipitation averages 1099.3 Millimeters. Mifflintown is located in USDA Plant Hardiness Zone 7a. 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 | -6.3 °C | 2.8 °C | 76.96 mm |
| February | -5.7 °C | 4.7 °C | 60.2 mm |
| March | -1.7 °C | 9.7 °C | 87.63 mm |
| April | 3.8 °C | 17.1 °C | 92.46 mm |
| May | 9.6 °C | 22.6 °C | 103.38 mm |
| June | 14.8 °C | 27.2 °C | 102.62 mm |
| July | 17.1 °C | 29.7 °C | 100.33 mm |
| August | 16.3 °C | 28.7 °C | 100.33 mm |
| September | 12.2 °C | 24.8 °C | 113.03 mm |
| October | 5.9 °C | 18.2 °C | 99.31 mm |
| November | 0.5 °C | 11.6 °C | 77.98 mm |
| December | -3.4 °C | 5.2 °C | 85.09 mm |
| Annual | 5.3 °C | 16.9 °C | 1099.32 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°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 |