Pennsylvania Frost Dates by Region

Pennsylvania’s average last spring frost falls anywhere from late March to mid-May, depending on where you live. Philadelphia gardeners get a head start as early as March 30, while folks up in the mountains near Erie or the Poconos might wait until May. That’s a five-week gap across the same state.

Getting your frost dates right is the foundation for everything else — when to start seeds indoors, when to transplant, and when to stop planting in fall. Here’s the data broken down by region and city so you can plan around your part of PA, not just a statewide average.

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What Are Frost Dates and Why Do They Matter?

Your last spring frost date is the average final day of the year when temperatures can dip to 32°F or below. After that date, the risk of frost drops enough that you can safely put tender plants like tomatoes and peppers in the ground.

Your first fall frost date is the flip side — the average date in autumn when freezing temps return. Between these two dates is your frost-free growing season, and in PA, that ranges from about 140 days in the mountains to over 230 days near Philadelphia.

These dates are based on 30-year climate normals tracked by NOAA. They’re averages, not guarantees. I’ve personally lost tomato transplants to a random May 8 frost in Central PA that “shouldn’t” have happened. So treat these dates as planning tools, not promises.

What Are the Frost Dates for Each PA Region?

Pennsylvania isn’t one climate — it’s at least four. Your frost dates depend on your USDA zone, elevation, and whether you’re closer to the coast, the mountains, or one of the Great Lakes.

Eastern PA (Philadelphia Area — Zones 6b–7a)

The mildest part of the state. The Philadelphia metro and surrounding counties enjoy the longest growing season in PA.

City	Last Spring Frost	First Fall Frost	Frost-Free Days
Philadelphia	March 30	November 17	~232
Allentown	April 14	October 19	~188
Reading	April 12	October 21	~192

Philadelphia is zone 7a — the warmest zone in Pennsylvania. If you’re in the Philly suburbs, you can push spring planting earlier and stretch fall harvests later than anywhere else in the state. Some years I’ve seen gardeners near the city still picking tomatoes in late October.

Central PA (Harrisburg Area — Zones 6a–6b)

The middle of the state transitions between the milder east and the cooler west. Harrisburg itself is relatively moderate, but move north toward State College or into the ridges and things get colder fast.

City	Last Spring Frost	First Fall Frost	Frost-Free Days
Harrisburg	April 10	October 28	~201
State College	May 3	October 5	~155
Williamsport	April 28	October 10	~165
York	April 14	October 22	~191

The spread here is wild — Harrisburg gets over 200 frost-free days, but State College loses almost 50 of them barely 60 miles north, due to elevation. If you’re in the valleys, you get a more forgiving season. On the ridges, plan like you’re a zone cooler than the map says.

Western PA (Pittsburgh Area — Zones 5b–6b)

Pittsburgh sits at the edge of where PA starts getting meaningfully colder. The surrounding suburbs and rural areas see later springs and earlier falls than the eastern half of the state.

City	Last Spring Frost	First Fall Frost	Frost-Free Days
Pittsburgh	April 20	October 23	~187
Johnstown	May 5	October 3	~151
Meadville	May 8	October 4	~149
Indiana	May 7	October 2	~148

Pittsburgh proper benefits from the urban heat island effect, so the city itself is a bit warmer than these numbers suggest. But once you’re out in rural Butler, Westmoreland, or Fayette counties — add a week or two to your spring planting dates to be safe.

Northern PA and Mountains (Zones 5a–5b)

This is the coldest growing region in Pennsylvania. The northern tier and mountain communities deal with late springs, early falls, and short growing seasons.

City	Last Spring Frost	First Fall Frost	Frost-Free Days
Erie	May 1	October 11	~163
Scranton	April 24	October 14	~174
Bradford	May 15	September 28	~136
Mount Pocono	May 10	October 1	~144

Erie is interesting — Lake Erie actually moderates temperatures, giving the city a slightly longer season than you’d expect for its latitude. But inland from the lake, you’re firmly in zone 5a territory with some of the shortest growing seasons in the state.

If you garden in this region, cold-hardy varieties and season extension tools are your best friends. A set of frost blankets or row covers can add 2–3 weeks to both ends of your season — easily the best $20–30 you’ll spend on your garden.

What Are All the Pennsylvania Frost Dates by City?

City	Region	USDA Zone	Last Spring Frost	First Fall Frost	Growing Season
Philadelphia	Eastern	7a	March 30	Nov 17	~232 days
Reading	Eastern	6b	April 12	Oct 21	~192 days
York	Central	6b	April 14	Oct 22	~191 days
Allentown	Eastern	6a	April 14	Oct 19	~188 days
Harrisburg	Central	6a	April 10	Oct 28	~201 days
Pittsburgh	Western	6a	April 20	Oct 23	~187 days
Scranton	Northern	5b	April 24	Oct 14	~174 days
Williamsport	Central	6a	April 28	Oct 10	~165 days
Erie	Northern	5b	May 1	Oct 11	~163 days
State College	Central	5b	May 3	Oct 5	~155 days
Johnstown	Western	5b	May 5	Oct 3	~151 days
Indiana	Western	5b	May 7	Oct 2	~148 days
Meadville	Western	5b	May 8	Oct 4	~149 days
Mount Pocono	Northern	5a	May 10	Oct 1	~144 days
Bradford	Northern	5a	May 15	Sep 28	~136 days

How to Use Frost Dates in Your Planting Plan

Knowing your frost dates is step one. Here’s how to actually apply them:

Counting Backward for Indoor Seed Starting

Most seed packets tell you to “start indoors 6–8 weeks before last frost.” That countdown starts from your last frost date, not a national average.

For example, if you’re in Pittsburgh (last frost April 20):
– Tomatoes (6–8 weeks before): Start indoors February 23 – March 9
– Peppers (8–10 weeks before): Start indoors February 9 – February 23
– Broccoli (4–6 weeks before): Start indoors March 9 – March 23

If you’re in Philadelphia (last frost March 30), bump all of those dates up by three weeks.

Fall Planting in Reverse

Your first fall frost date tells you when to stop planting — or more accurately, when to start counting backward for fall crops.

Take kale: it takes about 55 days from seed to harvest. If your first frost is October 15, you need seeds in the ground by mid-August at the latest. Most fall crops need to be planted in July or August, which catches a lot of people off guard.

The Two-Week Buffer Rule

Here’s a practical tip: add two weeks of buffer to both sides of your frost dates. Plant tender crops two weeks after your last frost date, and plan your final fall harvests two weeks before your first frost date.

Microclimates: When Your Yard Doesn’t Match the Map

• South-facing slopes warm up faster in spring and stay warmer into fall.
• Low spots and valley floors collect cold air. Frost settles in low areas first.
• Urban heat islands keep city gardens warmer than rural areas.
• Near water — gardens close to large bodies of water benefit from thermal moderation.
• Against a south-facing wall — the thermal mass radiates heat at night, protecting nearby plants from light frosts.

What Should You Do When a Late Frost Threatens?

• Cover tender plants with old sheets, frost blankets, or row covers the evening before a forecasted frost.
• Water the soil in the afternoon before a frost. Moist soil holds heat better than dry soil.
• Don’t cover with plastic directly on plants. Use fabric or keep plastic supported above the plant on stakes.
• Move containers indoors or into a garage for the night.

Frequently Asked Questions

Cool-season crops like onions and garlic go in the ground well before the last frost — check their individual planting guides for zone-specific dates.

How can I extend my growing season in Pennsylvania? Cold frames, row covers, and frost blankets can add 3–6 weeks to your season on both ends.

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