Duncannon, PA 17020 Frost Dates
17020, near Duncannon, PA: the frost window
Typically, the last spring freeze lands around 04/09, roughly 224 days out. Fall's first freeze usually shows up around 11/01, roughly 205 days after the last spring frost.
Zone 7a (0 to 5°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 Duncannon, not a forecast for this year.
Stretching the season past the first frost
Duncannon'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.
Why 04/09 isn't a guarantee
04/09 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/25 and only about 1 year in 10 sees frost after that.
Duncannon against the rest of the dataset
At roughly 205 frost-free days, Duncannon places 16,344 of 40,283 ZIP codes in this dataset. Within PA, it ranks 171 of 2,088.
Learn more
Two guides worth reading on 17020: the frost range, on how to read the range around Duncannon's dates instead of trusting one, and local microclimates, on what one yard in Duncannon can differ from the 17020 normal.