Frost dates / By state
Frost dates in Pennsylvania
NOAA 1991–2020 normals for a 32 °F freeze. Your own yard can run a little either side.
Short answer
Across 25 NOAA weather stations in Pennsylvania, the average last spring frost runs from April 2 at Philadelphia Intl Airport to May 18 at Bradford Rgnl Airport. The first fall frost comes as early as October 1 at Bradford Rgnl Airport and as late as November 10 at Philadelphia Intl Airport. Planting zones near these stations run from 5b to 7b.
Pennsylvania cities
- Frost dates in Philadelphia: last frost April 4, first frost November 7
- Frost dates in Pittsburgh: last frost April 18, first frost October 28
Find yours by ZIP code
The table below is by weather station. For the station nearest you, and your planting zone, type your ZIP code.
Pennsylvania frost dates by weather station
| Station | Last spring frost | First fall frost | Frost-free | Zone nearby |
|---|---|---|---|---|
| Allentown Intl Airport 390 ft | April 20 1 in 10 after May 6 | October 24 1 in 10 by October 8 | 187 days | 7a |
| Altoona Blair Co Airport 1,480 ft | April 23 1 in 10 after May 11 | October 21 1 in 10 by October 5 | 181 days | 6b |
| Avondale 2 N 400 ft | April 19 1 in 10 after May 3 | October 26 1 in 10 by October 11 | 190 days | 7a |
| Bradford Rgnl Airport 2,117 ft | May 18 1 in 10 after May 31 | October 1 1 in 10 by September 18 | 136 days | 5b |
| Clearfield Lawrence Airport 1,516 ft | May 4 1 in 10 after May 22 | October 11 1 in 10 by September 29 | 160 days | 6a |
| Doylestown Airport 394 ft | April 13 1 in 10 after April 27 | October 30 1 in 10 by October 15 | 200 days | 7a |
| Dubois Jefferson Co Airport 1,814 ft | May 6 1 in 10 after May 23 | October 14 1 in 10 by September 29 | 161 days | 6a |
| Erie Intl Airport 730 ft | April 26 1 in 10 after May 13 | November 4 1 in 10 by October 21 | 192 days | 6b |
| Harrisburg Cptl Cy Airport 340 ft | April 9 1 in 10 after April 25 | November 1 1 in 10 by October 16 | 206 days | 7a |
| Johnstown Cambria Co Airport 2,284 ft | April 29 1 in 10 after May 17 | October 21 1 in 10 by October 5 | 175 days | 6b |
| Lancaster Airport 403 ft | April 18 1 in 10 after May 5 | October 25 1 in 10 by October 10 | 190 days | 7a |
| Middletown Harrisburg Intl Airport 312 ft | April 9 1 in 10 after April 25 | November 2 1 in 10 by October 18 | 207 days | 7a |
| Mt Pocono Mountains Airport 1,916 ft | May 6 1 in 10 after May 23 | October 8 1 in 10 by September 27 | 155 days | 6a |
| Philadelphia Intl Airport 10 ft | April 2 1 in 10 after April 13 | November 10 1 in 10 by October 30 | 222 days | 7b |
| Philadelphia Ne Airport 100 ft | April 4 1 in 10 after April 17 | November 7 1 in 10 by October 24 | 217 days | 7b |
| Pittsburgh Allegheny Co Airport 1,248 ft | April 18 1 in 10 after May 6 | October 28 1 in 10 by October 14 | 193 days | 6b |
| Pittsburgh Intl Airport 1,203 ft | April 23 1 in 10 after May 12 | October 23 1 in 10 by October 9 | 183 days | 6b |
| Port Meadville Airport 1,400 ft | April 30 1 in 10 after May 18 | October 23 1 in 10 by October 6 | 176 days | 6a |
| Pottstown Limerick Airport 291 ft | April 20 1 in 10 after May 6 | October 23 1 in 10 by October 9 | 186 days | 7a |
| Reading Spaatz Fld 341 ft | April 14 1 in 10 after April 30 | October 29 1 in 10 by October 13 | 198 days | 7a |
| Selinsgrove Penn Vly Airport 444 ft | April 27 1 in 10 after May 12 | October 16 1 in 10 by October 3 | 172 days | 6b |
| Wilkes-Barre Intl Airport 930 ft | April 23 1 in 10 after May 10 | October 20 1 in 10 by October 4 | 180 days | 6b |
| Williamsport 520 ft | April 24 1 in 10 after May 11 | October 23 1 in 10 by October 6 | 182 days | 6b |
| Willow Grove NAS 361 ft | April 11 1 in 10 after April 27 | November 1 1 in 10 by October 17 | 204 days | 7a |
| York Airport 486 ft | April 27 1 in 10 after May 11 | October 18 1 in 10 by October 4 | 174 days | 6b |
The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. Stations are NOAA's main weather stations, mostly airports. “Zone nearby” is the USDA 2023 zone of the nearest ZIP code within 10 miles. NOAA counts the frost season from August to July, so in the warmest places the “first fall” freeze lands after New Year.
How these dates work
Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.
The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.
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Where the numbers come from
- USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture
- PRISM Climate Group, Oregon State University (zone data)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal
- NOAA, Normals calculation methodology (frost-freeze probability dates)
- US Census Bureau, 2025 ZCTA gazetteer (ZIP code centers)