Millheim, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.5 °C (low) to 15.2 °C (high). Annual precipitation averages 1075.2 Millimeters. Millheim 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.2 °C | 0.9 °C | 74.42 mm |
| February | -7.4 °C | 2.8 °C | 58.67 mm |
| March | -3.6 °C | 7.8 °C | 81.79 mm |
| April | 2.3 °C | 15.4 °C | 91.44 mm |
| May | 8.1 °C | 21.5 °C | 99.82 mm |
| June | 13.1 °C | 25.9 °C | 103.89 mm |
| July | 15.3 °C | 28.3 °C | 104.14 mm |
| August | 14.2 °C | 27.3 °C | 98.55 mm |
| September | 10.1 °C | 23.2 °C | 106.43 mm |
| October | 4.1 °C | 16.4 °C | 94.49 mm |
| November | -1.1 °C | 9.7 °C | 78.99 mm |
| December | -5.1 °C | 3.4 °C | 82.55 mm |
| Annual | 3.5 °C | 15.2 °C | 1075.18 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 |