Last spring frost
Apr 9
Frost Dates for Hummelstown, PA
First fall frost
Nov 2
Growing season
206 days
Hardiness zone
7a
In an average year around Hummelstown, PA, the last spring frost (32°F) is about Apr 9 and the first fall frost is about Nov 2, giving roughly a 206-day growing season. To be safe most years, wait until Mar 28 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) | May 7 | Apr 23 | Apr 9 |
| Freeze (32°F) | Apr 25 | Apr 9 | Mar 28 |
| Hard (28°F) | Apr 9 | Mar 30 | Mar 14 |
| Severe (24°F) | Mar 31 | Mar 17 | Mar 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 7 | May 2 | Apr 28 | Apr 25 | Apr 23 | Apr 20 | Apr 17 | Apr 14 | Apr 9 |
| 32°F | Apr 25 | Apr 18 | Apr 15 | Apr 11 | Apr 9 | Apr 7 | Apr 4 | Apr 1 | Mar 28 |
| 28°F | Apr 9 | Apr 5 | Apr 3 | Apr 1 | Mar 30 | Mar 27 | Mar 23 | Mar 19 | Mar 14 |
| 24°F | Mar 31 | Mar 27 | Mar 23 | Mar 20 | Mar 17 | Mar 14 | Mar 11 | Mar 8 | Mar 2 |
| 20°F | Mar 21 | Mar 17 | Mar 14 | Mar 11 | Mar 8 | Mar 5 | Mar 1 | Feb 26 | Feb 19 |
| 16°F | Mar 15 | Mar 9 | Mar 4 | Feb 28 | Feb 25 | Feb 21 | Feb 15 | Feb 10 | Feb 1 |
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 9 | Oct 22 | Nov 4 |
| Freeze (32°F) | Oct 18 | Nov 2 | Nov 15 |
| Hard (28°F) | Oct 31 | Nov 14 | Nov 29 |
| Severe (24°F) | Nov 10 | Nov 26 | Dec 13 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 9 | Oct 14 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 4 |
| 32°F | Oct 18 | Oct 24 | Oct 27 | Oct 31 | Nov 2 | Nov 4 | Nov 7 | Nov 10 | Nov 15 |
| 28°F | Oct 31 | Nov 4 | Nov 8 | Nov 11 | Nov 14 | Nov 16 | Nov 19 | Nov 23 | Nov 29 |
| 24°F | Nov 10 | Nov 16 | Nov 19 | Nov 23 | Nov 26 | Dec 1 | Dec 3 | Dec 7 | Dec 13 |
| 20°F | Nov 24 | Nov 30 | Dec 3 | Dec 7 | Dec 10 | Dec 15 | Dec 19 | Dec 24 | Dec 30 |
| 16°F | Dec 7 | Dec 13 | Dec 19 | Dec 22 | Dec 26 | Dec 30 | Jan 3 | Jan 10 | Jan 17 |
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: Middletown Harrisburg Intl Ap, Pa, about 5 miles away@if(!empty($station['elevation_ft'])), at 312 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 Hummelstown, PA?
On average, the last spring frost (32°F) around Hummelstown, PA is about Apr 9. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 28.
When is the first frost in the fall?
The first fall frost around Hummelstown, PA typically arrives about Nov 2. 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 9 on average, or Mar 28 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 206 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 17036 Planting calendar → Pennsylvania frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026