What Zone Is Pennsylvania
Pennsylvania spans USDA Hardiness Zones 5a to 7a by county. Find your zone and learn what perennials and vegetables to plant where in PA.
Key takeaways
- Philadelphia and suburban Delaware/Montgomery/Chester counties sit in Zone 7a — the warmest zone in Pennsylvania, where borderline tender plants like fig trees often overwinter
- Pittsburgh, Harrisburg, and most of central Pennsylvania fall in Zone 6a or 6b — the state's most common zone, with average annual low temperatures of -5°F to 0°F
- The Pocono Mountains, Endless Mountains, and Potter County plateau reach Zone 5a or 5b — where only cold-hardy perennials and short-season vegetable varieties succeed reliably
- Pennsylvania's zone boundaries run roughly east-west, with altitude causing more variation than latitude — a mountain ridge can drop a location from Zone 6b to 5b within 10 miles
- The USDA updated its official zone map in November 2023 — many Pennsylvania counties shifted half a zone warmer, so check the current map if using old zone data
What USDA growing zone is Pennsylvania?
Pennsylvania spans USDA Plant Hardiness Zones 5a through 7a, with the zone determined primarily by elevation and distance from the temperate influence of the Atlantic coast — not just latitude.
The state divides roughly into three zone bands:
| Region | Zone | Average Winter Low |
|---|---|---|
| Philadelphia metro and SE suburbs | 7a | 0°F to 5°F |
| Pittsburgh, Harrisburg, Lehigh Valley | 6a–6b | -5°F to 0°F |
| Pocono Mountains, Potter County plateau | 5a–5b | -15°F to -10°F |
The 2023 USDA update — the first major revision since 2012 — shifted many Pennsylvania locations half a zone warmer, reflecting climate data from 1991–2020 versus the older 1976–2005 baseline. If your garden guide was printed before 2023, verify your zone against the current USDA map.
Zone-by-zone breakdown
Zone 7a — Philadelphia metro and southeastern PA
Zone 7a covers Philadelphia proper plus most of Delaware, Chester, and Montgomery counties. Average winter minimum temperatures in this zone run from 0°F to 5°F.
Zone 7a is Pennsylvania’s warmest zone and allows:
- Fig trees (Ficus carica): overwinter outdoors with 12–18 inches of mulch at the base in Zone 7a; frequently die back to the roots in Zone 6b
- Crape myrtles (Lagerstroemia): survive as shrubs in Zone 7a but are not reliably winter-hardy in Zone 6b
- Gardenias: require Zone 7+ for outdoor survival
- Perennials rated Zone 6 and Zone 7 reliably survive without extra protection
Zone 7a’s last frost date in Philadelphia averages March 22 to April 7 — three to four weeks earlier than Pittsburgh or Harrisburg, giving Zone 7a gardeners a meaningful head start on warm-season crops.
Zone 6a and 6b — central Pennsylvania and Pittsburgh
Zone 6a covers roughly -10°F to -5°F winter lows. Zone 6b covers -5°F to 0°F. Together, these zones cover:
- Pittsburgh and Allegheny County (primarily 6a–6b)
- Harrisburg and the Susquehanna Valley (primarily 6b)
- Allentown, Bethlehem, the Lehigh Valley (6b)
- Erie and northwestern PA (6a near the lake, 5b away from it)
- Most of Lancaster and York counties (6b)
Zone 6 is Pennsylvania’s most common zone. Most standard perennials rated for Zone 5 or 6 perform reliably here without special protection. See full sun perennials for varieties that cover Zone 6 Pennsylvania gardens.
Vegetable timing in Zone 6 Pennsylvania:
| Crop | Seed start indoors | Transplant outside |
|---|---|---|
| Tomatoes | 8 weeks before last frost (late February) | After last frost (mid to late April) |
| Peppers | 10 weeks before last frost (mid-February) | After last frost, soil 65°F+ |
| Cucumbers | Direct sow or transplant late April–May | After last frost |
| Lettuce, spinach | 6 weeks before last frost | 4–6 weeks before last frost (direct sow March) |
| Garlic | Fall, 4–6 weeks before hard freeze | October or November |
See how to start a vegetable garden for a full Zone 6 Pennsylvania planting calendar.
Zone 5a and 5b — Pocono Mountains and northcentral plateau
Zone 5a covers -20°F to -15°F winter lows. Zone 5b covers -15°F to -10°F. In Pennsylvania, these zones appear:
- High elevations in the Pocono Mountains (Monroe, Wayne, Pike counties at higher altitudes)
- The Endless Mountains of Sullivan, Bradford, and Wyoming counties
- Potter County and the northcentral plateau — Pennsylvania’s coldest farming region
Zone 5 gardeners in Pennsylvania work with:
- Short growing seasons (last frost often May 10–25; first fall frost September 15–30)
- Limited perennial plant palette — plants must be rated Zone 4 or 5 to be reliable
- Aggressive mulching requirements for all overwintering perennials
For Zone 5 vegetable growing, short-season varieties are essential: Early Girl tomatoes (52 days) outperform standard Main Season varieties at these elevations.
How altitude affects zone in Pennsylvania
Altitude matters more than latitude in Pennsylvania. The state’s elevation ranges from sea level at the Delaware River in Philadelphia to 3,213 feet at Mount Davis in Somerset County.
A general rule: every 1,000-foot gain in elevation drops average temperatures by approximately 3°F — which translates to roughly half a USDA hardiness zone colder.
Practical examples:
- Pittsburgh city center (700 feet elevation): Zone 6b
- Laurel Highlands plateau (2,400 feet): Zone 5b–6a
- Mount Davis summit (3,213 feet): Zone 5a or colder
This explains why gardeners on opposite sides of a ridge in the same county can be in different zones. USDA zones covers how to assess your microsite beyond the official zone map number.
Pennsylvania microclimate factors
The official zone number is a starting point. These local factors can shift effective growing conditions one direction or another:
| Factor | Effect |
|---|---|
| South-facing slope | Up to 1 zone warmer — soil warms faster, frost drains away |
| North-facing slope | Up to 1 zone colder — frost pockets form, late to warm |
| Valley floor | Cold air drainage makes valley floors 5–10°F colder than surrounding hillsides on still nights |
| Urban heat island | Philadelphia city center may be 5–7°F warmer than surrounding suburbs |
| Lake Erie proximity | Erie county stays warmer in winter than interior PA at the same elevation |
| Forest windbreak | Reduces wind chill; allows more cold-tender plants on the protected side |
What to plant in Pennsylvania by zone
Zone 7a (Philadelphia metro)
Vegetables: Warm-season crops — how to grow tomatoes, peppers, eggplant, okra — perform well with a long season (last frost early April, first fall frost late October). Two successions of lettuce and spinach work in spring and fall.
Perennials: Zone 6 and 7 perennials are reliable. Gardenias, crape myrtles, and certain bamboos that are not reliable in Zone 6 can be attempted here.
Trees and shrubs: Fig trees, southern magnolia, and crape myrtle perform in Zone 7a Philadelphia without special protection.
Zone 6a–6b (central PA and Pittsburgh)
Vegetables: Standard warm-season crops with standard timing. Start tomatoes and peppers indoors in late February, transplant in mid-to-late April after last frost. Garlic planted in October yields in July.
Perennials: Most Zone 5 and 6 perennials perform reliably. See planting zones for a broader zone 6 plant selection framework.
Trees and shrubs: Japanese maple, flowering dogwood, Eastern redbud, ornamental grasses — all perform well in Zone 6 Pennsylvania.
Zone 5a–5b (Pocono and northcentral PA)
Vegetables: Short-season varieties only. Day-to-harvest time is critical: choose Early Girl (52 days) over standard-season tomatoes (75+ days). Season extenders — row cover, cold frames, black plastic mulch — are standard practice.
Perennials: Use only Zone 4 or 5-rated perennials. Hosta, daylily, black-eyed Susan, and purple coneflower are reliable. Lavender (Zone 5–6 varieties only), catmint, and salvia may need winter mulching.
Trees and shrubs: Stick to hardy species — lilac, forsythia, and native viburnums handle Zone 5 winters reliably.
Vegetable garden layout for Pennsylvania
Pennsylvania’s zone variety makes a zone-specific vegetable garden layout useful before ordering seeds. Key design principles for PA gardens:
- Zone 6 and 7: Full 4-foot wide raised beds; 18-inch spacing for tomatoes works; standard season varieties appropriate
- Zone 5: Narrower beds (2–3 feet) warm faster in spring; maximize south-facing orientation to extend season; row covers on hand for late spring cold snaps
Using best mulch for vegetable garden practices — 2–3 inches of organic mulch — stabilizes soil temperature and extends the effective growing season at both ends in all Pennsylvania zones.
How to find your exact Pennsylvania zone
- Go to planthardiness.ars.usda.gov — the official USDA map
- Enter your zip code
- Verify the zone shown matches your elevation and local conditions
- Check your county extension website — Penn State Extension publishes county-level frost date tables for all 67 counties
Penn State Extension is Pennsylvania’s primary gardening resource, with research-based guides for each region. Their publication “Vegetable Production for the Home Garden” (available free online) includes zone-specific planting calendars for every PA county.
Sarah Mitchell is a Master Gardener and garden writer based in the Pacific Northwest. She has been growing food and flowers for over 15 years across USDA zones 7 and 8.