Frost dates for Port Alexander, AK
At Port Alexander, the median last spring frost (32°F) is Apr 18 and the median first fall frost is Nov 5, for a typical growing season of 198 days. For a 90% chance that the last frost has passed, wait until May 5. Nearby ZIP codes are in USDA hardiness zone 8a.
- Apr 18Last spring frost (median)50% chance of 32°F after this date
- May 5Safer planting date10% chance of 32°F after this date
- Nov 5First fall frost (median)50% chance of 32°F by this date
- 198 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 25 | May 10 | May 25 |
| 32°F | Mar 31 | Apr 18 | May 5 |
| 28°F | Mar 4 | Mar 26 | Apr 11 |
| 24°F | Jan 24 | Mar 6 | Mar 27 |
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 29 | Oct 14 | Nov 1 |
| 32°F | Oct 16 | Nov 5 | Nov 25 |
| 28°F | Nov 4 | Nov 24 | Dec 26 |
| 24°F | Nov 16 | Dec 15 | Jan 25 |
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 | 155 days | 177 days |
| 32°F | 171 days | 198 days | 226 days |
| 28°F | 215 days | 243 days | 279 days |
| 24°F | 247 days | 285 days | 331 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 98% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 99836 | 8a | 10 to 15°F | 0 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 USC00507557, at 56.2472, -134.6447, elevation 4 m (12 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 68.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Little Port Walter (15 km)
- Point Baker (64 km)
- Sitka 1 NE (99 km)
- Sitka Airport (99 km)
- Hidden Falls Hatchery (109 km)
- Petersburg 1 (122 km)
- Klawock Airport (123 km)
- Craig (127 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.