Frost dates for Safe Harbor Dam, PA
At Safe Harbor Dam, the median last spring frost (32°F) is Apr 1 and the median first fall frost is Nov 10, for a typical growing season of 221 days. For a 90% chance that the last frost has passed, wait until Apr 13. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 1Last spring frost (median)50% chance of 32°F after this date
- Apr 13Safer planting date10% chance of 32°F after this date
- Nov 10First fall frost (median)50% chance of 32°F by this date
- 221 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Apr 1 | Apr 13 | May 3 |
| 32°F | Mar 18 | Apr 1 | Apr 13 |
| 28°F | Mar 6 | Mar 22 | Apr 1 |
| 24°F | Feb 25 | Mar 13 | Mar 25 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Oct 16 | Nov 1 | Nov 13 |
| 32°F | Oct 28 | Nov 10 | Nov 25 |
| 28°F | Nov 7 | Nov 22 | Dec 7 |
| 24°F | Nov 18 | Dec 4 | Dec 26 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 174 days | 198 days | 216 days |
| 32°F | 202 days | 221 days | 241 days |
| 28°F | 225 days | 244 days | 264 days |
| 24°F | 246 days | 267 days | 290 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 17516 | 7a | 0 to 5°F | 0 km |
| 17565 | 7a | 0 to 5°F | 6 km |
| 17551 | 7a | 0 to 5°F | 6 km |
| 17309 | 7a | 0 to 5°F | 8 km |
| 17582 | 7a | 0 to 5°F | 9 km |
| 17532 | 7a | 0 to 5°F | 11 km |
| 17302 | 7a | 0 to 5°F | 12 km |
| 17317 | 7a | 0 to 5°F | 12 km |
| 17368 | 7a | 0 to 5°F | 13 km |
| 17560 | 7a | 0 to 5°F | 14 km |
| 17366 | 7a | 0 to 5°F | 14 km |
| 17322 | 7a | 0 to 5°F | 15 km |
| 17518 | 7a | 0 to 5°F | 17 km |
| 17321 | 7a | 0 to 5°F | 20 km |
| 17352 | 7a | 0 to 5°F | 20 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00367732, at 39.9253, -76.3892, elevation 59 m (195 ft).
- Data quality: Representative (10+ years), 18 years of freeze data.
- Average days per year at or below 32°F: 87.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Lancaster 2ne Fltr Plant (17 km)
- Landisville 2 NW (22 km)
- Lancaster Airport (23 km)
- York 3 SSW Pump Station (31 km)
- New Holland 2 SE (32 km)
- Octoraro Lake (33 km)
- York Airport (41 km)
- Middletown Harrisburg Intl Airport (44 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.