Philadelphia, PA Frost Dates: Last Spring and First Fall Frost

Frost leaves Philadelphia on March 30 and comes back on November 17 when the odds are even, a window of 232 days for tender plants.

Even odds are a coin toss, so plan around the safer edges: one spring in ten still has a freeze on or after April 12, and one fall in ten has its first freeze by November 4. At 232 days, Philadelphia's typical season sits close to the 229 days median of the 100 cities on these pages.

The numbers belong to Phila Franklin Inst, NOAA station USC00366886, which sits 4.1 miles south-west of the Census Bureau's internal point for Philadelphia at an elevation of about 60 feet.

When is the last frost in Philadelphia?

One year in ten has a freeze on or after April 12. In nine years out of ten there is still a freeze on or after March 15, and half of years see one on or after March 30.

Only 28 days separate the earliest and latest of these dates, a tighter run than most of the 100 cities here, so the typical date is a fairly dependable guide in Philadelphia.

When is the first frost in Philadelphia?

NOAA's early fall date for Philadelphia is November 4, its even-odds date is November 17 and its late date is December 4; the first freeze has come by each of them in one, five and nine years out of ten.

From the earliest first freeze to the latest is 30 days, close to the middle of the pack.

The growing season in Philadelphia

The season is about as long as the middle of these pages. Seasons here barely vary: the typical year gives 232 days and a short one still gives 214 days, only 18 days less, a steadier record than most cities on these pages.

These figures are NOAA's own counts of freeze-free days across its simulated years, which is why they can differ a little from the days between the two typical dates. At Phila Franklin Inst a night at or below 32°F turns up in 100% of years, which means these dates apply every winter.

When a hard freeze reaches Philadelphia

Hard freezes trail the light ones by 12 days in fall (November 29 against November 17) and by 13 days in spring (March 17 against March 30). One spring in ten still has a 28°F night on or after March 31, and one fall in ten sees the first by November 12.

What this means for planting in Philadelphia

University of New Hampshire Extension sorts vegetables by how they cope with cold. Cool-season crops go out before the last frost: counting from March 30, cabbage transplants go in on March 2 and lettuce from March 2 to March 9. Tender crops wait until it has passed, with peppers going out on April 13 and beans sown on or after March 30. The University of New Hampshire Extension sheet gives peas no frost count at all; sow them as soon as the soil thaws.

Counting from the late date, April 12, instead of the typical one delays every after-frost crop by 13 days. That is the price of a one-in-ten spring that most years will not need.

Of the 34 crops in the fall planner, 32 still have a July-or-later last planting day in Philadelphia once NC State Extension's days to harvest and University of Georgia Extension's harvest allowance of 18 days are counted back from frost. The other 2 do not. The slowest crop that still fits is collard greens, which needs 118 days before the early first frost and so must be in by July 9.

Worked example: planting broccoli for fall in Philadelphia

Take fall broccoli in Philadelphia. NC State Extension lists up to 80 days from transplant to harvest, and University of Georgia Extension adds a harvest allowance of 18 days, so the plants need 98 days before the first frost. Counting back from the typical first frost, November 17, the last planting day is August 11. Counting back from the early date, November 4, it is July 29.

With only 13 days between the two last days, Philadelphia gardeners can plan on either without much difference.

Spring is the other end of the same arithmetic: University of New Hampshire Extension sets cabbage-family transplants out two to four weeks before the last frost, which from March 30 puts cabbage out on March 2.

The weather station behind these dates

4.1 miles south-west of the city's internal point, the station is close but not on top of Philadelphia.

At about 60 feet, it ranks above 14 and below 84 of the 100 stations used for these pages. Its completeness flag is S, which NOAA uses for a standard record.

Because the Census file has no elevation for Philadelphia, we cannot say how far your yard is above or below this station. When yours is clearly higher or lower, open the nearby stations in the frost dates tool and favor the colder one.

Nearby cities and their frost dates

Philadelphia sits in a cluster: Newark, NJ is only 71 miles away, and the other two cities below are not much farther, so gaps in their dates come from local setting.

• Newark, NJ lies 71 miles north-east of Philadelphia. Typical last frost April 4, first frost November 6, 216 days between; spring frost lingers 5 days longer than in Philadelphia, and the frost-free season is 16 days shorter than Philadelphia's.
• New York, NY lies 77 miles north-east of Philadelphia. Typical last frost April 1, first frost November 19, 233 days between; its last frost falls within a few days of Philadelphia's, and frost-free days differ from Philadelphia's by less than a week.
• Baltimore, MD lies 93 miles south-west of Philadelphia. Typical last frost March 24, first frost November 21, 244 days between; spring frost ends 6 days sooner than in Philadelphia, and the frost-free season is 12 days longer than Philadelphia's.

Put the frost dates to work

Open the frost dates tool with this station already chosen to see the whole ladder of probability dates, or try the nearby stations in the same list. The spring planting planner and the fall planting planner turn the same dates into a full crop list, and the hardiness zone lookup tells you which perennials will survive the winter.

All the cities on these pages are listed by state on the city frost dates index.

Where these numbers come from

Every frost and freeze date comes from the station's entry in NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), with no adjustment, and NOAA's documentation explains what each probability means. The city and its internal point come from the Census Bureau's 2024 Gazetteer of places, and the ranking by size from the Census Bureau's Vintage 2024 city and town population estimates, which put Philadelphia at 1,573,916 people.

The planting dates apply the count rules in University of New Hampshire Extension, NC State Extension and University of Georgia Extension to this station's dates, with nothing added. Our methodology describes the tests behind every number.

NOAA's dates say how often frost has come, not when it will. Check the forecast before planting and keep a cover on hand.