Frost dates for S Mountain, PA
At S Mountain, the median last spring frost (32°F) is Apr 27 and the median first fall frost is Oct 20, for a typical growing season of 177 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 27Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 20First fall frost (median)50% chance of 32°F by this date
- 177 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 24 | May 7 | May 24 |
| 32°F | Apr 13 | Apr 27 | May 14 |
| 28°F | Mar 31 | Apr 13 | May 1 |
| 24°F | Mar 19 | Apr 1 | Apr 13 |
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 | Sep 24 | Oct 8 | Oct 21 |
| 32°F | Oct 6 | Oct 20 | Nov 2 |
| 28°F | Oct 17 | Nov 1 | Nov 14 |
| 24°F | Oct 30 | Nov 11 | Nov 28 |
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 | 132 days | 154 days | 173 days |
| 32°F | 155 days | 177 days | 196 days |
| 28°F | 178 days | 202 days | 221 days |
| 24°F | 205 days | 224 days | 246 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 |
|---|---|---|---|
| 17261 | 7a | 0 to 5°F | 1 km |
| 17237 | 7a | 0 to 5°F | 4 km |
| 17222 | 7a | 0 to 5°F | 5 km |
| 17247 | 7a | 0 to 5°F | 9 km |
| 17268 | 7a | 0 to 5°F | 10 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 USC00368308, at 39.8508, -77.5039, elevation 463 m (1,520 ft).
- Data quality: Representative (10+ years), 15 years of freeze data.
- Average days per year at or below 32°F: 129.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Cashtown 1s (14 km)
- Chambersburg 1 ESE (15 km)
- Biglerville (23 km)
- Shippensburg (23 km)
- Eisenhower Nhs (24 km)
- Hanover 4 SW (41 km)
- Bloserville 1 N (47 km)
- Carlisle Water Plant (50 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.