Frost dates for Main Bay, AK
At Main Bay, the median last spring frost (32°F) is May 19 and the median first fall frost is Oct 6, for a typical growing season of 139 days. For a 90% chance that the last frost has passed, wait until Jun 4. Nearby ZIP codes are in USDA hardiness zones 5a to 8a.
- May 19Last spring frost (median)50% chance of 32°F after this date
- Jun 4Safer planting date10% chance of 32°F after this date
- Oct 6First fall frost (median)50% chance of 32°F by this date
- 139 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 24 | Jun 4 | Jun 20 |
| 32°F | May 2 | May 19 | Jun 4 |
| 28°F | Apr 11 | Apr 28 | May 11 |
| 24°F | Mar 31 | Apr 13 | Apr 29 |
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 11 | Sep 24 | Oct 5 |
| 32°F | Sep 24 | Oct 6 | Oct 22 |
| 28°F | Oct 3 | Oct 20 | Nov 4 |
| 24°F | Oct 17 | Nov 1 | Nov 19 |
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 | 92 days | 111 days | 127 days |
| 32°F | 119 days | 139 days | 161 days |
| 28°F | 154 days | 176 days | 197 days |
| 24°F | 182 days | 203 days | 225 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 |
|---|---|---|---|
| 99693 | 7a | 0 to 5°F | 37 km |
| 99587 | 5b | -15 to -10°F | 66 km |
| 99574 | 5a | -20 to -15°F | 72 km |
| 99605 | 5b | -15 to -10°F | 85 km |
| 99631 | 5a | -20 to -15°F | 85 km |
| 99540 | 5b | -15 to -10°F | 86 km |
| 99677 | 8a | 10 to 15°F | 88 km |
| 99664 | 5b | -15 to -10°F | 88 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 USC00505604, at 60.5181, -148.0930, elevation 17 m (57 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 172.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Wally Noerenberg Hatchery (31 km)
- Whittier (43 km)
- Portage Glacier V C (50 km)
- Port San Juan (52 km)
- Cannery Creek (64 km)
- Seward 19n (71 km)
- Moose Pass 3nw (73 km)
- Alyeska (74 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.