When Is the Last Frost in Pennsylvania?
The average last spring frost in Pennsylvania falls between April 11 and May 10 for most ZIP codes, with a statewide median of April 27. At the average date a later frost is still a coin flip, so tender plants wait for the safer 90% date.
| City | Last frost | 90% safe after | First frost | Growing season |
|---|---|---|---|---|
| Philadelphia | Mar 30 | Apr 12 | Nov 17 | 232 days |
| Pittsburgh | Apr 18 | May 6 | Oct 28 | 193 days |
| Allentown | Apr 20 | May 6 | Oct 24 | 184 days |
| Reading | Apr 14 | Apr 30 | Oct 29 | 197 days |
| Erie | Apr 26 | May 13 | Nov 4 | 192 days |
| Bethlehem | Apr 20 | May 6 | Oct 24 | 184 days |
| Scranton | Apr 23 | May 10 | Oct 20 | 178 days |
| Lancaster | Apr 19 | May 7 | Oct 24 | 186 days |
| Harrisburg | Apr 15 | May 2 | Oct 23 | 189 days |
| York | Apr 26 | May 13 | Oct 19 | 177 days |
| Altoona | Apr 25 | May 11 | Oct 21 | 176 days |
| State College | Apr 20 | May 6 | Oct 26 | 187 days |
| Chester | Mar 30 | Apr 9 | Nov 16 | 230 days |
| Hazleton | Apr 30 | May 18 | Oct 22 | 175 days |
| Williamsport | Apr 25 | May 12 | Oct 24 | 181 days |
| Lebanon | Apr 20 | May 7 | Oct 25 | 185 days |
| Pottstown | Apr 20 | May 6 | Oct 23 | 186 days |
| Chambersburg | Apr 18 | May 5 | Oct 25 | 188 days |
| New Castle | Apr 30 | May 19 | Oct 23 | 175 days |
| St. Marys | May 14 | May 29 | Oct 6 | 143 days |
Last and first frost: 50% (median) dates of the last spring and first fall 32 °F night. 90% safe after: only a 10% chance of a later spring frost. First frost dates in January fall in the following winter. Each city uses the NOAA station nearest the ZIP code closest to its center.
Across all 160 Pennsylvania weather stations with frost records, median last frost dates run from March 30 at Marcus Hook, PA to May 24 at Kane 1 NNE, PA. Elevation, valleys that collect cold air and distance from large water bodies explain most of the spread, so a garden a few miles from a listed city can differ by a week or more. The ZIP code lookup above uses the same NOAA data as the frost date calculator for every US ZIP code.
When Is the First Frost in Pennsylvania?
The average first fall frost in Pennsylvania arrives between October 5 and November 4 for most ZIP codes, with a median of October 21. Tomatoes, peppers, basil and squash are damaged at 32 °F, so harvest or cover them before then.
Fall frost can come early: Philadelphia has a 10% chance of frost before November 4, Pittsburgh has a 10% chance of frost before October 14 and Allentown has a 10% chance of frost before October 8. Hardy crops such as kale, spinach and cabbage tolerate light frosts and keep producing after the first frost date.
When to Plant Tomatoes in Pennsylvania?
Transplant tomatoes in Pennsylvania 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: Apr 6 – Apr 13 in Philadelphia, Apr 25 – May 2 in Pittsburgh and Apr 27 – May 4 in Allentown. Start seeds indoors 6 to 8 weeks before the last frost.
| City | Start seeds indoors | Transplant outdoors | Lowest-risk transplant |
|---|---|---|---|
| Philadelphia | Feb 2 – Feb 16 | Apr 6 – Apr 13 | after Apr 12 |
| Pittsburgh | Feb 21 – Mar 7 | Apr 25 – May 2 | after May 6 |
| Allentown | Feb 23 – Mar 9 | Apr 27 – May 4 | after May 6 |
| Reading | Feb 17 – Mar 3 | Apr 21 – Apr 28 | after Apr 30 |
| Erie | Mar 1 – Mar 15 | May 3 – May 10 | after May 13 |
| Bethlehem | Feb 23 – Mar 9 | Apr 27 – May 4 | after May 6 |
| Scranton | Feb 26 – Mar 12 | Apr 30 – May 7 | after May 10 |
| Lancaster | Feb 22 – Mar 8 | Apr 26 – May 3 | after May 7 |
| Harrisburg | Feb 18 – Mar 4 | Apr 22 – Apr 29 | after May 2 |
| York | Mar 1 – Mar 15 | May 3 – May 10 | after May 13 |
| Altoona | Feb 28 – Mar 14 | May 2 – May 9 | after May 11 |
| State College | Feb 23 – Mar 9 | Apr 27 – May 4 | after May 6 |
| Chester | Feb 2 – Feb 16 | Apr 6 – Apr 13 | after Apr 9 |
| Hazleton | Mar 5 – Mar 19 | May 7 – May 14 | after May 18 |
| Williamsport | Feb 28 – Mar 14 | May 2 – May 9 | after May 12 |
| Lebanon | Feb 23 – Mar 9 | Apr 27 – May 4 | after May 7 |
| Pottstown | Feb 23 – Mar 9 | Apr 27 – May 4 | after May 6 |
| Chambersburg | Feb 21 – Mar 7 | Apr 25 – May 2 | after May 5 |
| New Castle | Mar 5 – Mar 19 | May 7 – May 14 | after May 19 |
| St. Marys | Mar 19 – Apr 2 | May 21 – May 28 | after May 29 |
Indoors: 6–8 weeks before the average last frost. Outdoors: 1–2 weeks after it. Lowest-risk: after the date with only a 10% chance of a later frost. Rules of thumb; check the 10-day forecast and wait for soil near 60 °F.
Tomatoes stall below about 50 °F at night and are killed by frost, so a week or two of waiting after the average date costs little. The tomato plant care guide covers light, watering and feeding once plants are in the ground.
What Can You Plant in Philadelphia and When?
Philadelphia's average last frost of March 30 anchors its spring planting calendar: peas and spinach go in from February 16, broccoli and lettuce transplants from March 2, and tomatoes, peppers and squash after April 6.
| Crop | Start seeds indoors | Plant outdoors | Frost tolerance |
|---|---|---|---|
| Peas | — | Feb 16 – Mar 2direct sow, 4–6 weeks before last frost | hardy |
| Spinach | — | Feb 16 – Mar 9direct sow, 3–6 weeks before last frost | hardy |
| Radishes | — | Feb 23 – Mar 9direct sow, 3–5 weeks before last frost | hardy |
| Onions (sets) | — | Mar 2 – Mar 16plant, 2–4 weeks before last frost | hardy |
| Potatoes | — | Mar 2 – Mar 16plant, 2–4 weeks before last frost | half-hardy |
| Broccoli & cabbage | Feb 2 – Feb 16 | Mar 2 – Mar 16transplant, 2–4 weeks before last frost | hardy |
| Lettuce | Feb 16 – Mar 2 | Mar 2 – Mar 16transplant, 2–4 weeks before last frost | hardy |
| Beets | — | Mar 2 – Mar 16direct sow, 2–4 weeks before last frost | half-hardy |
| Carrots | — | Mar 9 – Mar 16direct sow, 2–3 weeks before last frost | half-hardy |
| Tomatoes | Feb 2 – Feb 16 | Apr 6 – Apr 13transplant, 1–2 weeks after last frost | tender |
| Basil | Feb 2 – Feb 16 | Apr 6 – Apr 20transplant, 1–3 weeks after last frost | tender |
| Peppers | Jan 19 – Feb 2 | Apr 13 – Apr 20transplant, 2–3 weeks after last frost | tender |
| Eggplant | Jan 19 – Feb 2 | Apr 13 – Apr 20transplant, 2–3 weeks after last frost | tender |
| Green beans | — | Apr 6 – Apr 20direct sow, 1–3 weeks after last frost | tender |
| Sweet corn | — | Apr 6 – Apr 20direct sow, 1–3 weeks after last frost | tender |
| Cucumbers | Mar 2 – Mar 9 | Apr 6 – Apr 20transplant, 1–3 weeks after last frost | tender |
| Squash & zucchini | Mar 2 – Mar 9 | Apr 6 – Apr 20transplant, 1–3 weeks after last frost | tender |
| Watermelon | Mar 2 – Mar 9 | Apr 13 – Apr 20transplant, 2–3 weeks after last frost | tender |
Dates for Philadelphia (last frost Mar 30, NOAA station Phila Franklin Inst, PA, 4 miles from ZIP 19140). General rules of thumb; wait for soil near 50 °F for most seeds and 60 °F for beans, corn and squash.
How Long Is the Growing Season in Pennsylvania?
The frost-free growing season in Pennsylvania lasts about 148 to 205 days for most ZIP codes, with a median of 176 days. Among the listed cities, St. Marys has the shortest season at 143 days and Philadelphia the longest at 232.
Season length decides which varieties ripen: compare it with the “days to maturity” on seed packets, counted from transplanting for tomatoes and peppers. NOAA stations in Pennsylvania range from 126 days at Kane 1 NNE, PA to 232 days at Phila Franklin Inst, PA. Planning beds before the season starts helps in short seasons — a plant spacing calculator for vegetable beds shows how many transplants fit.
What Hardiness Zones Are in Pennsylvania?
Pennsylvania spans USDA hardiness zones 5b to 8a, with zone 6b the most common. Zones describe winter cold and decide which perennials survive, while frost dates set when to plant annual vegetables and flowers.
The Pennsylvania planting zone map with the zone of each city shows how the zones are spread across the state and which plants are hardy in all of them.
Frequently Asked Questions
- When is the last frost in Pennsylvania?
- The average last spring frost in Pennsylvania falls between April 11 and May 10 for most ZIP codes, with a statewide median of April 27. Among major cities it ranges from March 30 in Philadelphia to May 14 in St. Marys.
- When is the last frost in Philadelphia, Pennsylvania?
- Philadelphia's average last spring frost is March 30, and by April 12 the chance of a later frost drops to 10%. Its first fall frost averages November 17, giving a 232-day growing season (NOAA station Phila Franklin Inst, PA).
- When should you plant tomatoes in Pennsylvania?
- Transplant tomatoes in Pennsylvania 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: Apr 6 – Apr 13 in Philadelphia, Apr 25 – May 2 in Pittsburgh and Apr 27 – May 4 in Allentown. Start seeds indoors 6 to 8 weeks before the last frost.
- When is the first frost in Pennsylvania?
- The average first fall frost in Pennsylvania arrives between October 5 and November 4 for most ZIP codes, with a median of October 21. Harvest tender crops such as tomatoes, peppers and basil before then or cover them on cold nights.
- How long is the growing season in Pennsylvania?
- The frost-free growing season in Pennsylvania lasts about 148 to 205 days for most ZIP codes, with a median of 176 days, from 143 days in St. Marys to 232 days in Philadelphia.
Frost data: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals (32 °F freeze dates by probability). ZIP code and city locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. Planting windows are general rules of thumb. PlantoScan is not affiliated with or endorsed by these agencies.