Philadelphia, PA 19171 Frost Dates
19171, near Philadelphia, PA: the frost window
The last spring frost here typically falls around 04/15, about 230 days from today. Fall's first freeze usually shows up around 10/31, roughly 199 days after the last spring frost.
Zone 7b (5 to 10°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Philadelphia, not a forecast for this year.
Stretching the season past the first frost
Philadelphia's growing season runs out in roughly 9 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Philadelphia's last frost
04/15 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/01 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/01 and only about 1 year in 10 sees frost after that.
Philadelphia against the rest of the dataset
At roughly 199 frost-free days, Philadelphia places 17,948 of 40,283 ZIP codes in this dataset. Within PA, it ranks 261 of 2,088.
Learn more
Two guides worth reading on 19171: zone vs. frost date, on why Zone 7b and Philadelphia's frost date answer different questions, and the frost range, on how to read the range around Philadelphia's dates instead of trusting one.