Horsham, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.2 °C (low) to 17.7 °C (high). Annual precipitation averages 1230.1 Millimeters. Horsham 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 | -4.6 °C | 4.5 °C | 87.88 mm |
| February | -3.7 °C | 6 °C | 68.07 mm |
| March | 0.2 °C | 10.6 °C | 105.41 mm |
| April | 5.8 °C | 17.2 °C | 95.76 mm |
| May | 11.3 °C | 22.6 °C | 106.17 mm |
| June | 16.4 °C | 27.6 °C | 112.52 mm |
| July | 19.4 °C | 30.2 °C | 122.68 mm |
| August | 18.5 °C | 29.2 °C | 125.48 mm |
| September | 14.5 °C | 25.6 °C | 110.49 mm |
| October | 7.9 °C | 18.9 °C | 102.36 mm |
| November | 2.4 °C | 12.8 °C | 83.57 mm |
| December | -1.7 °C | 7.2 °C | 109.73 mm |
| Annual | 7.2 °C | 17.7 °C | 1230.12 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 7a : -17.8°C to -15°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |