Frost dates for Portage Glacier V C, AK
At Portage Glacier V C, the median last spring frost (32°F) is May 27 and the median first fall frost is Sep 12, for a typical growing season of 106 days. For a 90% chance that the last frost has passed, wait until Jun 11. Nearby ZIP codes are in USDA hardiness zones 5a to 7a.
- May 27Last spring frost (median)50% chance of 32°F after this date
- Jun 11Safer planting date10% chance of 32°F after this date
- Sep 12First fall frost (median)50% chance of 32°F by this date
- 106 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 |
|---|---|---|---|
| 32°F | May 12 | May 27 | Jun 11 |
| 28°F | Apr 21 | May 4 | May 23 |
| 24°F | Apr 6 | Apr 19 | May 4 |
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 |
|---|---|---|---|
| 32°F | Aug 24 | Sep 12 | Sep 30 |
| 28°F | Sep 13 | Oct 1 | Oct 16 |
| 24°F | Sep 27 | Oct 11 | Oct 30 |
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 | 38 days | 61 days | 89 days |
| 32°F | 81 days | 106 days | 131 days |
| 28°F | 123 days | 145 days | 167 days |
| 24°F | 151 days | 175 days | 198 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 99587 | 5b | -15 to -10°F | 20 km |
| 99605 | 5b | -15 to -10°F | 36 km |
| 99540 | 5b | -15 to -10°F | 36 km |
| 99693 | 7a | 0 to 5°F | 44 km |
| 99631 | 5a | -20 to -15°F | 48 km |
| 99577 | 5a | -20 to -15°F | 50 km |
| 99507 | 5a | -20 to -15°F | 56 km |
| 99516 | 5b | -15 to -10°F | 57 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 USW00026492, at 60.7850, -148.8389, elevation 31 m (103 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 171.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Whittier (8 km)
- Alyeska (24 km)
- Wally Noerenberg Hatchery (41 km)
- Hope (45 km)
- Moose Pass 3nw (45 km)
- Main Bay (50 km)
- Eagle River Nature Center (55 km)
- Seward 19n (55 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.