Arnold, 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 16.7 °C (high). Annual precipitation averages 1088.6 Millimeters. Arnold 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.9 °C | 3 °C | 85.34 mm |
| February | -5.3 °C | 4.6 °C | 66.8 mm |
| March | -1.6 °C | 9.6 °C | 82.04 mm |
| April | 4.1 °C | 17.1 °C | 90.17 mm |
| May | 10.1 °C | 22.7 °C | 100.58 mm |
| June | 15.2 °C | 27.1 °C | 114.05 mm |
| July | 17.4 °C | 29.2 °C | 112.78 mm |
| August | 16.7 °C | 28.4 °C | 93.98 mm |
| September | 12.8 °C | 24.7 °C | 98.3 mm |
| October | 6.5 °C | 17.8 °C | 80.52 mm |
| November | 1.1 °C | 11.1 °C | 80.01 mm |
| December | -3 °C | 5.3 °C | 84.07 mm |
| Annual | 5.7 °C | 16.7 °C | 1088.64 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 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 |