Frost dates for Norristown, PA
At Norristown, the median last spring frost (32°F) is Apr 8 and the median first fall frost is Oct 31, for a typical growing season of 203 days. For a 90% chance that the last frost has passed, wait until Apr 23. Nearby ZIP codes are in USDA hardiness zones 7a to 7b.
- Apr 8Last spring frost (median)50% chance of 32°F after this date
- Apr 23Safer planting date10% chance of 32°F after this date
- Oct 31First fall frost (median)50% chance of 32°F by this date
- 203 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Apr 6 | Apr 22 | May 9 |
| 32°F | Mar 28 | Apr 8 | Apr 23 |
| 28°F | Mar 15 | Mar 31 | Apr 12 |
| 24°F | Mar 2 | Mar 19 | Apr 3 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Oct 6 | Oct 20 | Nov 3 |
| 32°F | Oct 14 | Oct 31 | Nov 12 |
| 28°F | Oct 27 | Nov 10 | Nov 22 |
| 24°F | Nov 7 | Nov 21 | Dec 8 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 159 days | 180 days | 201 days |
| 32°F | 183 days | 203 days | 222 days |
| 28°F | 206 days | 224 days | 246 days |
| 24°F | 227 days | 249 days | 271 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 19405 | 7b | 5 to 10°F | 1 km |
| 19401 | 7a | 0 to 5°F | 2 km |
| 19428 | 7b | 5 to 10°F | 4 km |
| 19406 | 7a | 0 to 5°F | 4 km |
| 19462 | 7b | 5 to 10°F | 5 km |
| 19403 | 7a | 0 to 5°F | 6 km |
| 19422 | 7a | 0 to 5°F | 7 km |
| 19444 | 7b | 5 to 10°F | 7 km |
| 19087 | 7a | 0 to 5°F | 8 km |
| 19085 | 7a | 0 to 5°F | 8 km |
| 19035 | 7b | 5 to 10°F | 8 km |
| 19010 | 7b | 5 to 10°F | 10 km |
| 19031 | 7b | 5 to 10°F | 10 km |
| 19333 | 7a | 0 to 5°F | 11 km |
| 19118 | 7b | 5 to 10°F | 11 km |
| 19041 | 7b | 5 to 10°F | 12 km |
| 19008 | 7b | 5 to 10°F | 15 km |
| 19073 | 7a | 0 to 5°F | 16 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00366370, at 40.1097, -75.3369, elevation 19 m (62 ft).
- Data quality: Representative (10+ years), 20 years of freeze data.
- Average days per year at or below 32°F: 107.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Phoenixville 1 E (13 km)
- Graterford 1 E (15 km)
- Willow Grove NAS (19 km)
- Phila Franklin Inst (22 km)
- Pottstown Limerick Airport (24 km)
- Sellersville (27 km)
- Philadelphia NE Airport (28 km)
- Philadelphia Intl Airport (28 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.