Pennsylvania Frost Dates and Planting Zones
Across 2,174 ZIP codes we matched to a NOAA weather station, Pennsylvania’s last spring frost (50% risk, 32°F) ranges from May 24 near Kane 1nne to Mar 30 near Phila Franklin Inst. First fall frost runs from Sep 27 near Clarence to Nov 17 near Phila Franklin Inst. Look up your exact ZIP code on the frost date tool for a station-matched result and hardiness zone.
Frost dates by city in Pennsylvania
The 12 weather stations covering the most PA ZIP codes, at the 50% and 10% probability levels (32°F threshold). The 10% date is later and safer to plant after; the 50% date is the typical planning date.
| Station | Last frost (50%) | Last frost (10%) | First frost (50%) | First frost (10%) |
|---|---|---|---|---|
| Phila Franklin Inst | Mar 30 | Apr 12 | Nov 17 | Nov 4 |
| Wilkes-barre Intl ap | Apr 23 | May 10 | Oct 20 | Oct 4 |
| Pittsburgh Allegheny co ap | Apr 18 | May 6 | Oct 28 | Oct 14 |
| Mahanoy City 2 n | Apr 30 | May 18 | Oct 22 | Oct 7 |
| Norristown | Apr 8 | Apr 23 | Oct 31 | Oct 14 |
| Harrisburg 1 ne | Apr 15 | May 2 | Oct 23 | Oct 7 |
| Doylestown ap | Apr 13 | Apr 27 | Oct 30 | Oct 15 |
| Allentown Intl ap | Apr 20 | May 6 | Oct 24 | Oct 8 |
| Lehighton 1ssw | Apr 21 | May 9 | Oct 23 | Oct 7 |
| Graterford 1 e | Apr 24 | May 9 | Oct 15 | Oct 1 |
| Putneyville 2 se Dam | May 10 | May 28 | Oct 12 | Sep 30 |
| Erie Intl ap | Apr 26 | May 13 | Nov 4 | Oct 21 |
USDA hardiness zones in Pennsylvania
Share of Pennsylvania ZIP codes in each 2023 USDA Plant Hardiness Zone. 63.3% of PA ZIP codes moved to a different zone between the 2012 and 2023 maps, mostly warming as winter lows trended up.
| Zone (2023) | Share of PA ZIPs |
|---|---|
| 5b | 3.2% |
| 6a | 24.2% |
| 6b | 36.1% |
| 7a | 29.1% |
| 7b | 7.2% |
| 8a | 0.1% |
Climate is shifting
Averaged across PA stations with both normals periods, the last spring frost now lands about 2 days earlier than the 1981–2010 normal. First fall frost now lands about 4 days later, stretching or shrinking the frost-free season depending on the station.
Plan around your Pennsylvania frost dates
Once you know your local last and first frost, these guides help you time the work around them: