Frost dates for Anchorage Forecast Office, AK
At Anchorage Forecast Office, the median last spring frost (32°F) is May 5 and the median first fall frost is Sep 29, for a typical growing season of 147 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 5Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Sep 29First fall frost (median)50% chance of 32°F by this date
- 147 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 | May 8 | May 17 | May 28 |
| 32°F | Apr 25 | May 5 | May 14 |
| 28°F | Apr 11 | Apr 22 | May 3 |
| 24°F | Apr 1 | Apr 11 | Apr 24 |
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 6 | Sep 19 | Oct 1 |
| 32°F | Sep 17 | Sep 29 | Oct 13 |
| 28°F | Sep 27 | Oct 9 | Oct 23 |
| 24°F | Oct 5 | Oct 19 | Nov 2 |
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 | 107 days | 123 days | 138 days |
| 32°F | 130 days | 147 days | 164 days |
| 28°F | 152 days | 169 days | 186 days |
| 24°F | 172 days | 188 days | 206 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 |
|---|---|---|---|
| 99502 | 5b | -15 to -10°F | 1 km |
| 99515 | 5a | -20 to -15°F | 7 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 USC00500275, at 61.1561, -149.9847, elevation 40 m (131 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 188.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Anchorage Lake Hood Airport (3 km)
- Anchorage Intl Airport (3 km)
- Anchorage Merrill Field (10 km)
- Campbell Creek Sci Center (11 km)
- Anchorage Rabbit Creek #2 (14 km)
- Anchorage Upper De Armoun (16 km)
- Glen Alps (17 km)
- Fort Richardson Water Plant (20 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.