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Frost Dates in Pennsylvania
First and last frost dates across Pennsylvania, computed from 62 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
Apr 30
statewide median · range Apr 2–May 24
First fall frost
Oct 20
statewide median · range Sep 28–Nov 10
Growing season
173 days
median · range 126–224
Stations used
62
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Philadelphia | Phila Intl Ap · 6 mi | Apr 2 (cautious: Apr 13) | Nov 10 | 224 days | Apr 16 |
| Pittsburgh | Pittsburgh Allegheny Co Ap · 7 mi | Apr 18 (cautious: May 6) | Oct 28 | 193 days | May 2 |
| Harrisburg | Harrisburg Capital City Ap · 4 mi | Apr 9 (cautious: Apr 25) | Nov 1 | 205 days | Apr 23 |
How frost varies across Pennsylvania
Spring frost timing spans about 52 days across the state. Phila in southeastern Pennsylvania typically sees its last spring frost around April 2, while Kane in northwestern Pennsylvania doesn't clear frost until about May 24. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Pennsylvania
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 14 for the statewide median. Check your city's row above rather than the statewide median: a 52-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 62 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Pennsylvania?
The statewide median last spring frost is April 30, but it ranges from April 2 to May 24 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Pennsylvania?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 14 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Pennsylvania?
The median growing season across 62 NOAA stations is 173 days, ranging from 126 to 224 days by location.
Why do frost dates vary so much within Pennsylvania?
Frost timing follows latitude, elevation, and local terrain. Across Pennsylvania, last spring frost dates span about 52 days — from around April 2 near Phila to May 24 near Kane. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.