Last spring frost
Mar 30
Frost Dates for Philadelphia, PA
First fall frost
Nov 17
Growing season
232 days
Hardiness zone
7b
In an average year around Philadelphia, PA, the last spring frost (32°F) is about Mar 30 and the first fall frost is about Nov 17, giving roughly a 232-day growing season. To be safe most years, wait until Mar 15 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Apr 23 | Apr 8 | Mar 27 |
| Freeze (32°F) | Apr 12 | Mar 30 | Mar 15 |
| Hard (28°F) | Mar 31 | Mar 17 | Mar 1 |
| Severe (24°F) | Mar 22 | Mar 8 | Feb 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 23 | Apr 19 | Apr 15 | Apr 11 | Apr 8 | Apr 6 | Apr 3 | Apr 1 | Mar 27 |
| 32°F | Apr 12 | Apr 7 | Apr 4 | Apr 1 | Mar 30 | Mar 27 | Mar 24 | Mar 20 | Mar 15 |
| 28°F | Mar 31 | Mar 27 | Mar 23 | Mar 20 | Mar 17 | Mar 15 | Mar 11 | Mar 7 | Mar 1 |
| 24°F | Mar 22 | Mar 17 | Mar 14 | Mar 11 | Mar 8 | Mar 5 | Mar 1 | Feb 25 | Feb 18 |
| 20°F | Mar 14 | Mar 8 | Mar 5 | Mar 1 | Feb 25 | Feb 20 | Feb 15 | Feb 8 | Feb 2 |
| 16°F | Mar 5 | Feb 27 | Feb 21 | Feb 15 | Feb 9 | Feb 4 | Jan 31 | Jan 25 | Jan 16 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 23 | Nov 5 | Nov 20 |
| Freeze (32°F) | Nov 4 | Nov 17 | Dec 4 |
| Hard (28°F) | Nov 12 | Nov 29 | Dec 18 |
| Severe (24°F) | Nov 24 | Dec 14 | Jan 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 23 | Oct 28 | Oct 31 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 20 |
| 32°F | Nov 4 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 28 | Dec 4 |
| 28°F | Nov 12 | Nov 17 | Nov 21 | Nov 26 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 18 |
| 24°F | Nov 24 | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 19 | Dec 22 | Dec 27 | Jan 2 |
| 20°F | Dec 7 | Dec 13 | Dec 19 | Dec 23 | Dec 27 | Dec 31 | Jan 4 | Jan 9 | Jan 16 |
| 16°F | Dec 19 | Dec 28 | Jan 1 | Jan 5 | Jan 9 | Jan 13 | Jan 17 | Jan 23 | Feb 1 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Phila Franklin Inst, Pa, about 1.7 miles away@if(!empty($station['elevation_ft'])), at 60 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Philadelphia, PA?
On average, the last spring frost (32°F) around Philadelphia, PA is about Mar 30. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 15.
When is the first frost in the fall?
The first fall frost around Philadelphia, PA typically arrives about Nov 17. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Mar 30 on average, or Mar 15 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 232 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 19121 Planting calendar → Pennsylvania frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026