Frost dates / Pennsylvania / Harrisburg
Frost dates in Harrisburg, PA
The station on this page is HARRISBURG 1 NE, PA US (USC00363698), 0.9 miles from the city point. Population in the Census 2024 estimate is 50,649.
Zone 7aUSDA average annual extreme minimum 0°F to 5°F, from ZIP 17120 (0.8 miles from the city point used on this page).
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Last 32°F in spring
NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.
| Probability | Date | How to read it |
|---|---|---|
| 90% | April 1 | Earlier date. A last 32°F on or after this day is common. |
| 50% | April 15 | Median. |
| 10% | May 2 | Later date. A last 32°F on or after this day is uncommon. |
First 32°F in fall
NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.
| Probability | Date | How to read it |
|---|---|---|
| 10% | October 7 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | October 23 | Median. |
| 90% | November 7 | Later date. A first 32°F on or before this day is common. |
32°F growing-season length
Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.
| Probability the season is at least this long | Days |
|---|---|
| 10% | 210 |
| 50% | 189 |
| 90% | 167 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | April 16 | April 3 | March 19 |
| First, on or before | October 20 | November 5 | November 21 |
| Season at least | 236 days | 214 days | 193 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | May 15 | April 30 | April 14 |
| First, on or before | September 28 | October 12 | October 28 |
| Season at least | 184 days | 165 days | 143 days |
Station HARRISBURG 1 NE, PA US (USC00363698). Completeness flag R, 22 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 128 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.
Planting calendar for Harrisburg · Zone 7a
Check a crop against this station
Harrisburg, PA
Zone 7aAverage annual extreme minimum 0°F to 5°F
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Pennsylvania. Nearest qualified station: HARRISBURG 1 NE, PA US (USC00363698), 0.9 miles. Median last 32°F April 15. Median first 32°F October 23. The 50% growing-season length is 189 days.
Open the ZIP page · Crop guides for Pennsylvania
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | May 2 | April 15 | April 1 |
| First 32°F on or before | October 7 | October 23 | November 7 |
Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.
Planting calendar
Windows below are from Penn State Extension, Starting Your Summer Vegetable Garden—Seeds or Transplants?, retrieved 2026-10-10. The page gives dates for much of Pennsylvania, not for named regions. Spinach is the crop placed in a named month, April, and that month is read as April 1 through April 30. Phrases such as “early April,” “mid-April to late May,” and “late May to early June” stay phrases, because the page does not give them a day. Crops the page times only as “after the danger of frost has passed” or “early spring,” with no month, are left off these windows.
Date checks use your device’s calendar and appear after the page loads.