Last spring frost
Apr 18
Frost Dates for Port Alexander, AK
First fall frost
Nov 5
Growing season
198 days
In an average year around Port Alexander, AK, the last spring frost (32°F) is about Apr 18 and the first fall frost is about Nov 5, giving roughly a 198-day growing season. To be safe most years, wait until Mar 31 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | May 25 | May 10 | Apr 25 |
| Freeze (32°F) | May 5 | Apr 18 | Mar 31 |
| Hard (28°F) | Apr 11 | Mar 26 | Mar 4 |
| Severe (24°F) | Mar 27 | Mar 6 | Jan 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 25 | May 18 | May 16 | May 13 | May 10 | May 7 | May 4 | Apr 30 | Apr 25 |
| 32°F | May 5 | Apr 30 | Apr 26 | Apr 22 | Apr 18 | Apr 14 | Apr 10 | Apr 6 | Mar 31 |
| 28°F | Apr 11 | Apr 5 | Apr 1 | Mar 29 | Mar 26 | Mar 21 | Mar 17 | Mar 12 | Mar 4 |
| 24°F | Mar 27 | Mar 21 | Mar 15 | Mar 10 | Mar 6 | Mar 2 | Feb 22 | Feb 9 | Jan 24 |
| 20°F | Mar 17 | Mar 8 | Mar 2 | Feb 24 | Feb 14 | Feb 4 | Jan 27 | Jan 14 | Dec 31 |
| 16°F | Mar 9 | Feb 28 | Feb 13 | Feb 4 | Jan 27 | Jan 18 | Jan 12 | Jan 2 | Dec 24 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 29 | Oct 14 | Nov 1 |
| Freeze (32°F) | Oct 16 | Nov 5 | Nov 25 |
| Hard (28°F) | Nov 4 | Nov 24 | Dec 26 |
| Severe (24°F) | Nov 16 | Dec 15 | Jan 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 3 | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 21 | Oct 26 | Nov 1 |
| 32°F | Oct 16 | Oct 23 | Oct 28 | Nov 1 | Nov 5 | Nov 9 | Nov 13 | Nov 18 | Nov 25 |
| 28°F | Nov 4 | Nov 9 | Nov 15 | Nov 20 | Nov 24 | Nov 29 | Dec 3 | Dec 10 | Dec 26 |
| 24°F | Nov 16 | Nov 25 | Dec 1 | Dec 6 | Dec 15 | Dec 24 | Jan 1 | Jan 8 | Jan 25 |
| 20°F | Dec 1 | Dec 9 | Dec 21 | Dec 28 | Jan 1 | Jan 9 | Jan 19 | Jan 30 | Feb 20 |
| 16°F | Dec 10 | Dec 23 | Dec 31 | Jan 5 | Jan 12 | Jan 19 | Jan 29 | Feb 9 | Feb 28 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Port Alexander, Ak, about 0.3 miles away@if(!empty($station['elevation_ft'])), at 12 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Port Alexander, AK?
On average, the last spring frost (32°F) around Port Alexander, AK is about Apr 18. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 31.
When is the first frost in the fall?
The first fall frost around Port Alexander, AK typically arrives about Nov 5. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Apr 18 on average, or Mar 31 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 198 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 99836 Planting calendar → Alaska frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026