Allentown, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.8 °C (low) to 16.9 °C (high). Annual precipitation averages 1244.6 Millimeters. Allentown is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.9 °C | 3.3 °C | 89.15 mm |
| February | -5.2 °C | 4.9 °C | 74.93 mm |
| March | -1.2 °C | 9.7 °C | 96.01 mm |
| April | 4.6 °C | 16.6 °C | 94.23 mm |
| May | 10.1 °C | 22.2 °C | 103.89 mm |
| June | 15.3 °C | 26.9 °C | 120.65 mm |
| July | 17.9 °C | 29.5 °C | 120.9 mm |
| August | 16.9 °C | 28.4 °C | 130.81 mm |
| September | 12.8 °C | 24.8 °C | 122.43 mm |
| October | 6.3 °C | 18.1 °C | 102.62 mm |
| November | 1 °C | 11.8 °C | 84.07 mm |
| December | -2.9 °C | 6 °C | 104.9 mm |
| Annual | 5.8 °C | 16.9 °C | 1244.59 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |