Last spring frost
Apr 2
Frost Dates for Swarthmore, PA
First fall frost
Nov 10
Growing season
224 days
Hardiness zone
7b
In an average year around Swarthmore, PA, the last spring frost (32°F) is about Apr 2 and the first fall frost is about Nov 10, giving roughly a 224-day growing season. To be safe most years, wait until Mar 19 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 28 | Apr 13 | Apr 1 |
| Freeze (32°F) | Apr 13 | Apr 2 | Mar 19 |
| Hard (28°F) | Apr 3 | Mar 22 | Mar 7 |
| Severe (24°F) | Mar 26 | Mar 12 | Feb 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 28 | Apr 22 | Apr 18 | Apr 15 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Apr 1 |
| 32°F | Apr 13 | Apr 8 | Apr 6 | Apr 3 | Apr 2 | Mar 31 | Mar 29 | Mar 24 | Mar 19 |
| 28°F | Apr 3 | Mar 31 | Mar 28 | Mar 25 | Mar 22 | Mar 19 | Mar 16 | Mar 12 | Mar 7 |
| 24°F | Mar 26 | Mar 22 | Mar 18 | Mar 15 | Mar 12 | Mar 9 | Mar 6 | Mar 2 | Feb 24 |
| 20°F | Mar 18 | Mar 13 | Mar 8 | Mar 5 | Mar 1 | Feb 26 | Feb 21 | Feb 14 | Feb 5 |
| 16°F | Mar 7 | Mar 1 | Feb 24 | Feb 19 | Feb 13 | Feb 8 | Feb 3 | Jan 30 | Jan 20 |
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 18 | Oct 31 | Nov 12 |
| Freeze (32°F) | Oct 30 | Nov 10 | Nov 24 |
| Hard (28°F) | Nov 7 | Nov 23 | Dec 8 |
| Severe (24°F) | Nov 17 | Dec 4 | Dec 23 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 18 | Oct 23 | Oct 26 | Oct 28 | Oct 31 | Nov 2 | Nov 4 | Nov 8 | Nov 12 |
| 32°F | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 24 |
| 28°F | Nov 7 | Nov 12 | Nov 16 | Nov 19 | Nov 23 | Nov 26 | Nov 29 | Dec 2 | Dec 8 |
| 24°F | Nov 17 | Nov 23 | Nov 28 | Dec 1 | Dec 4 | Dec 9 | Dec 13 | Dec 17 | Dec 23 |
| 20°F | Nov 30 | Dec 6 | Dec 12 | Dec 17 | Dec 21 | Dec 25 | Dec 31 | Jan 3 | Jan 11 |
| 16°F | Dec 14 | Dec 23 | Dec 29 | Jan 1 | Jan 4 | Jan 8 | Jan 14 | Jan 19 | Jan 29 |
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: Philadelphia Intl Ap, Pa, about 6.5 miles away@if(!empty($station['elevation_ft'])), at 10 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 Swarthmore, PA?
On average, the last spring frost (32°F) around Swarthmore, PA is about Apr 2. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 19.
When is the first frost in the fall?
The first fall frost around Swarthmore, PA typically arrives about Nov 10. 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 Apr 2 on average, or Mar 19 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 224 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 19081 Planting calendar → Pennsylvania frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026