Frost dates for Middletown Harrisburg Intl Airport, PA
At Middletown Harrisburg Intl Airport, the median last spring frost (32°F) is Apr 9 and the median first fall frost is Nov 2, for a typical growing season of 206 days. For a 90% chance that the last frost has passed, wait until Apr 25. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 9Last spring frost (median)50% chance of 32°F after this date
- Apr 25Safer planting date10% chance of 32°F after this date
- Nov 2First fall frost (median)50% chance of 32°F by this date
- 206 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 9 | Apr 23 | May 7 |
| 32°F | Mar 28 | Apr 9 | Apr 25 |
| 28°F | Mar 14 | Mar 30 | Apr 9 |
| 24°F | Mar 2 | Mar 17 | Mar 31 |
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 9 | Oct 22 | Nov 4 |
| 32°F | Oct 18 | Nov 2 | Nov 15 |
| 28°F | Oct 31 | Nov 14 | Nov 29 |
| 24°F | Nov 10 | Nov 26 | Dec 13 |
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 | 163 days | 183 days | 202 days |
| 32°F | 185 days | 206 days | 224 days |
| 28°F | 211 days | 230 days | 249 days |
| 24°F | 234 days | 254 days | 276 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 |
|---|---|---|---|
| 17034 | 7a | 0 to 5°F | 3 km |
| 17057 | 7a | 0 to 5°F | 3 km |
| 17319 | 7a | 0 to 5°F | 5 km |
| 17036 | 7a | 0 to 5°F | 8 km |
| 17370 | 7a | 0 to 5°F | 9 km |
| 17502 | 7a | 0 to 5°F | 13 km |
| 17022 | 7a | 0 to 5°F | 13 km |
| 17345 | 7a | 0 to 5°F | 14 km |
| 17033 | 7a | 0 to 5°F | 14 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 USW00014711, at 40.1936, -76.7633, elevation 95 m (312 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 101.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Harrisburg Cptl Cy Airport (8 km)
- Harrisburg 1 NE (13 km)
- Lebanon 2 W (30 km)
- Dehart Dam (30 km)
- Landisville 2 NW (30 km)
- York 3 SSW Pump Station (31 km)
- York Airport (32 km)
- Carlisle Water Plant (36 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.