What Planting Zones Are in Pennsylvania?
Pennsylvania spans USDA hardiness zones 5b to 8a, where the average coldest winter night ranges from −15 °F to 15 °F (−26.1 °C to −9.4 °C). Zone 6b covers the most ZIP codes, 36%, and zones 6a to 7a together cover 89% of the state.
- Zone 5b3% · 68 ZIPs
- Zone 6a24% · 510 ZIPs
- Zone 6b36% · 761 ZIPs
- Zone 7a29% · 613 ZIPs
- Zone 7b7% · 153 ZIPs
- Zone 8a<1% · 3 ZIPs
Bars show each zone's share of the 2,108 Pennsylvania ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Pennsylvania Cities In?
Philadelphia is in zone 7b, Pittsburgh is in zone 6b, Allentown is in zone 7a and Reading is in zone 7a. The table lists the zone, winter low and average frost dates for 20 Pennsylvania cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Philadelphia | 19140 | 7b | 5 °F to 10 °F | Mar 30 | Nov 17 |
| Pittsburgh | 15219 | 6b | −5 °F to 0 °F | Apr 18 | Oct 28 |
| Allentown | 18102 | 7a | 0 °F to 5 °F | Apr 20 | Oct 24 |
| Reading | 19602 | 7a | 0 °F to 5 °F | Apr 14 | Oct 29 |
| Erie | 16501 | 7a | 0 °F to 5 °F | Apr 26 | Nov 4 |
| Bethlehem | 18018 | 7a | 0 °F to 5 °F | Apr 20 | Oct 24 |
| Scranton | 18503 | 6b | −5 °F to 0 °F | Apr 23 | Oct 20 |
| Lancaster | 17603 | 7a | 0 °F to 5 °F | Apr 19 | Oct 24 |
| Harrisburg | 17120 | 7a | 0 °F to 5 °F | Apr 15 | Oct 23 |
| York | 17401 | 7a | 0 °F to 5 °F | Apr 26 | Oct 19 |
| Altoona | 16602 | 6b | −5 °F to 0 °F | Apr 25 | Oct 21 |
| State College | 16802 | 6b | −5 °F to 0 °F | Apr 20 | Oct 26 |
| Chester | 19013 | 7b | 5 °F to 10 °F | Mar 30 | Nov 16 |
| Hazleton | 18201 | 6b | −5 °F to 0 °F | Apr 30 | Oct 22 |
| Williamsport | 17702 | 6b | −5 °F to 0 °F | Apr 25 | Oct 24 |
| Lebanon | 17046 | 7a | 0 °F to 5 °F | Apr 20 | Oct 25 |
| Pottstown | 19464 | 7a | 0 °F to 5 °F | Apr 20 | Oct 23 |
| Chambersburg | 17202 | 7a | 0 °F to 5 °F | Apr 18 | Oct 25 |
| New Castle | 16101 | 6a | −10 °F to −5 °F | Apr 30 | Oct 23 |
| St. Marys | 15857 | 5b | −15 °F to −10 °F | May 14 | Oct 6 |
Zone: 2023 USDA ZIP code table for the ZIP code nearest each city's Census center point. Frost dates: 50% (median) dates from the nearest NOAA station, 1991–2020 normals. Cities: the largest Pennsylvania places by 2024 Census population estimates, spread across the state, plus the largest place in each common zone. Large cities can span two half zones.
Which Parts of Pennsylvania Are in Each Zone?
Zone 5b, the coldest Pennsylvania zone, covers 3% of ZIP codes around St. Marys, Bradford and Ridgway. Zone 8a, the warmest, covers <1% around Ridley Park and Eddystone. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 5b | −15 °F to −10 °F | 3% (68) | St. Marys, Bradford, Ridgway, Kane |
| Zone 6a | −10 °F to −5 °F | 24% (510) | New Castle, Hermitage, Sharon, Meadville |
| Zone 6b | −5 °F to 0 °F | 36% (761) | Pittsburgh, Scranton, Altoona, State College |
| Zone 7a | 0 °F to 5 °F | 29% (613) | Allentown, Reading, Erie, Bethlehem |
| Zone 7b | 5 °F to 10 °F | 7% (153) | Philadelphia, Chester, Yeadon, Lansdowne |
| Zone 8a | 10 °F to 15 °F | <1% (3) | Ridley Park, Eddystone |
Places: incorporated places with 1,000+ residents, assigned the zone of the ZIP code nearest their Census center point.
What Do the Hardiness Zones Mean for Pennsylvania Gardeners?
A Pennsylvania gardener in zone 8a sees winter lows about 25 °F milder than one in zone 5b, so a shrub or perennial that thrives in one part of the state can die in another. Choose plants rated to your own ZIP code's zone or colder.
Hardiness zones follow latitude, elevation and large bodies of water rather than state lines. Higher ground and inland valleys that trap cold air usually sit in colder half zones, while cities, coasts and large lakes moderate winter lows. Within Pennsylvania, a plant labelled “zones 6–7” survives winter in at least 89% of ZIP codes, but plants at the edge of their range benefit from mulch and a sheltered spot. Enter a ZIP code in the USDA hardiness zone finder by ZIP code to check your exact half zone before buying perennials.
A zone describes winter cold only. Summer heat, humidity, rainfall and soil decide whether a cold-hardy plant thrives, and planting dates for vegetables follow frost dates, not zones: two Pennsylvania towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Pennsylvania?
219 plants in PlantoScan's catalogue are hardy in every zone from 6a to 7a, the zones that cover 89% of Pennsylvania ZIP codes. Popular examples include hydrangea, peony and daisy.
Hydrangea
Hydrangea macrophylla
Zone 5 – 9
AI generated
Peony
Paeonia lactiflora
Zone 3 – 8
AI generated
- DaisyBellis perennisPlantoScan
Daisy
Bellis perennis
Zone 4a – 8b
Chrysanthemum
Chrysanthemum morifolium
Zone 5a – 9b
PlantoscanAI generated
Poppy
Papaver somniferum
Zone 3a – 9b
AI generated
Carnation
Dianthus caryophyllus
Zone 5a – 9b
AI generated
Daffodil
Narcissus poeticus
Zone 3 – 8
AI generated
Azalea
Azalea indica
Zone 6a – 9b
AI generated
Arugula
Eruca sativa
Zone 5a – 10b
AI generated
Hardiness ranges come from PlantoScan's plant database; gardeners in Pennsylvania's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Pennsylvania?
Across most Pennsylvania ZIP codes, the average last spring frost falls between April 11 and May 10, from March 30 in Philadelphia to May 14 in St. Marys. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Pennsylvania cities include the safer 90% planting date, the fall frost date, growing season length and a tomato planting table for each city.
Frequently Asked Questions
- What planting zone is Pennsylvania?
- Pennsylvania spans USDA hardiness zones 5b to 8a on the 2023 USDA Plant Hardiness Zone Map. Zone 6b is the most common, covering 36% of the state's 2,108 ZIP codes, and zones 6a to 7a together cover 89%.
- What hardiness zone is Philadelphia, Pennsylvania?
- Philadelphia is in USDA hardiness zone 7b (ZIP 19140), where the average coldest winter night reaches 5 °F to 10 °F. Its average last spring frost is March 30 and its first fall frost November 17.
- What hardiness zone is Pittsburgh, Pennsylvania?
- Pittsburgh is in USDA hardiness zone 6b (ZIP 15219), where the average coldest winter night reaches −5 °F to 0 °F. Its average last spring frost is April 18 and its first fall frost October 28.
- What hardiness zone is Allentown, Pennsylvania?
- Allentown is in USDA hardiness zone 7a (ZIP 18102), where the average coldest winter night reaches 0 °F to 5 °F. Its average last spring frost is April 20 and its first fall frost October 24.
- What is the coldest hardiness zone in Pennsylvania?
- Zone 5b (−15 °F to −10 °F) is the coldest zone in Pennsylvania, found in 68 ZIP codes around St. Marys and Bradford. The warmest is zone 8a (10 °F to 15 °F), around Ridley Park and Eddystone.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code table, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, used without changes. Frost dates: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. City locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. PlantoScan is not affiliated with or endorsed by these agencies.