Norristown, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.1 °C (low) to 18 °C (high). Annual precipitation averages 1222.5 Millimeters. Norristown 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.6 °C | 4.6 °C | 87.88 mm |
| February | -3.8 °C | 6.1 °C | 73.15 mm |
| March | 0.1 °C | 10.8 °C | 106.43 mm |
| April | 5.7 °C | 17.7 °C | 95.5 mm |
| May | 11.2 °C | 23.1 °C | 103.12 mm |
| June | 16.5 °C | 28.1 °C | 111 mm |
| July | 19.3 °C | 30.6 °C | 115.57 mm |
| August | 18.4 °C | 29.7 °C | 120.4 mm |
| September | 14.3 °C | 26.1 °C | 113.03 mm |
| October | 7.7 °C | 19.2 °C | 102.62 mm |
| November | 2.2 °C | 13 °C | 82.55 mm |
| December | -1.7 °C | 7.4 °C | 111.25 mm |
| Annual | 7.1 °C | 18 °C | 1222.5 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 |