Last spring frost
May 5
Frost Dates for Old Harbor, AK
First fall frost
Oct 3
Growing season
151 days
In an average year around Old Harbor, AK, the last spring frost (32°F) is about May 5 and the first fall frost is about Oct 3, giving roughly a 151-day growing season. To be safe most years, wait until Apr 19 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) | Jun 9 | May 26 | May 10 |
| Freeze (32°F) | May 21 | May 5 | Apr 19 |
| Hard (28°F) | May 3 | Apr 18 | Apr 4 |
| Severe (24°F) | Apr 20 | Apr 4 | Mar 19 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 9 | Jun 3 | Jun 1 | May 29 | May 26 | May 23 | May 20 | May 16 | May 10 |
| 32°F | May 21 | May 16 | May 12 | May 8 | May 5 | May 2 | Apr 30 | Apr 25 | Apr 19 |
| 28°F | May 3 | Apr 28 | Apr 24 | Apr 21 | Apr 18 | Apr 14 | Apr 11 | Apr 8 | Apr 4 |
| 24°F | Apr 20 | Apr 14 | Apr 10 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 26 | Mar 19 |
| 20°F | Apr 7 | Apr 2 | Mar 31 | Mar 28 | Mar 25 | Mar 21 | Mar 16 | Mar 10 | Feb 28 |
| 16°F | Mar 31 | Mar 26 | Mar 20 | Mar 15 | Mar 9 | Mar 3 | Feb 25 | Feb 12 | Jan 29 |
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 8 | Sep 21 | Oct 2 |
| Freeze (32°F) | Sep 22 | Oct 3 | Oct 17 |
| Hard (28°F) | Oct 1 | Oct 17 | Nov 5 |
| Severe (24°F) | Oct 16 | Nov 3 | Nov 23 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 8 | Sep 13 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 26 | Sep 29 | Oct 2 |
| 32°F | Sep 22 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 12 | Oct 17 |
| 28°F | Oct 1 | Oct 5 | Oct 9 | Oct 13 | Oct 17 | Oct 21 | Oct 25 | Oct 30 | Nov 5 |
| 24°F | Oct 16 | Oct 23 | Oct 28 | Nov 1 | Nov 3 | Nov 7 | Nov 12 | Nov 17 | Nov 23 |
| 20°F | Nov 1 | Nov 4 | Nov 10 | Nov 15 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 8 |
| 16°F | Nov 11 | Nov 21 | Nov 26 | Dec 1 | Dec 4 | Dec 9 | Dec 14 | Dec 21 | Jan 1 |
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: Kodiak Ap, Ak, about 48.3 miles away@if(!empty($station['elevation_ft'])), at 80 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 Old Harbor, AK?
On average, the last spring frost (32°F) around Old Harbor, AK is about May 5. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 19.
When is the first frost in the fall?
The first fall frost around Old Harbor, AK typically arrives about Oct 3. 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 May 5 on average, or Apr 19 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 151 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 99643 Planting calendar → Alaska frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026