Unalaska, AK frost dates
Last spring frostMay 6median date
First fall frostOct 18median date
Growing season165 daysfrost-free
Hardiness zone8aZone 8a
How Unalaska compares
- In 8 years out of 10, the last spring frost in Unalaska falls between April 23 and May 22, a 29-day window. The first fall frost falls between September 20 and November 5.
- The median last frost is 15 days earlier than the Alaska median of May 21.
- Its 165-day growing season is longer than 83% of the 165 Alaska places with a regular frost season (state median 124 days).
- The last frost is 38 days later than the zone 8a median of Mar 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 8a chart.
- The weather station records an average of 112 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 23 |
| 50% (median) | May 6 |
| 10% (safe for tender plants) | May 22 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 20 |
| 50% (median) | October 18 |
| 90% (late) | November 5 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Unalaska, AK
Unalaska, AK frost dates — last frost May 6, first frost Oct 18, zone 8a. whenisthelastfrost.com
Crop
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Start indoors: Feb 11 to Feb 25Transplant outside: Apr 8 to Apr 22
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Mar 11 to Mar 25Transplant outside: May 13 to May 27
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Sow outdoors: Apr 8 to May 13Plant for fall: Aug 23 to Sep 20
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 8 to Apr 22Plant for fall: Aug 9 to Aug 30
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10Sow outdoors: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Mar 25 to Apr 15Plant for fall: Jul 26 to Aug 16
Sow outdoors: Mar 25 to Apr 15Plant for fall: Aug 23 to Sep 13
Sow outdoors: Apr 1 to May 13Plant for fall: Sep 6 to Sep 27
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to May 27Sow outdoors: May 13 to May 27Plant for fall: Aug 2 to Aug 16
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27Plant for fall: Aug 9 to Aug 23
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to Jun 3
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 15 to May 13Plant for fall: Aug 9 to Aug 23
Sow outdoors: Apr 15 to May 6
Sow outdoors: Apr 22 to May 20Plant for fall: Aug 9 to Aug 23
Sow outdoors: Apr 22 to May 13Plant for fall: Aug 23 to Sep 13
Sow outdoors: May 13 to Jun 3Plant for fall: Aug 2 to Aug 16
Sow outdoors: May 13 to May 27
Transplant outside: May 20 to Jun 10
Plant for fall: Oct 4 to Nov 8
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Unalaska, AK
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 11 – Feb 25 | Apr 8 – Apr 22 | — | — |
| Peppers | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Eggplant | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Tomatoes | Mar 11 – Mar 25 | May 13 – May 27 | — | — |
| Lettuce | Mar 11 – Mar 25 | Apr 15 – Apr 29 | Apr 8 – May 13 | Aug 23 – Sep 20 |
| Kale | Mar 11 – Mar 25 | Apr 8 – Apr 22 | Apr 8 – Apr 22 | Aug 9 – Aug 30 |
| Broccoli | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jul 12 – Aug 2 |
| Cabbage | Mar 11 – Mar 25 | Apr 15 – Apr 29 | — | Jul 12 – Aug 2 |
| Cauliflower | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jul 12 – Aug 2 |
| Okra | Mar 25 – Apr 8 | May 27 – Jun 10 | May 27 – Jun 10 | — |
| Basil | Mar 25 – Apr 8 | May 13 – May 27 | — | — |
| Peas | — | — | Mar 25 – Apr 15 | Jul 26 – Aug 16 |
| Spinach | — | — | Mar 25 – Apr 15 | Aug 23 – Sep 13 |
| Radishes | — | — | Apr 1 – May 13 | Sep 6 – Sep 27 |
| Cucumbers | Apr 8 – Apr 15 | May 20 – May 27 | May 13 – May 27 | Aug 2 – Aug 16 |
| Zucchini & Summer Squash | Apr 8 – Apr 15 | — | May 13 – May 27 | Aug 9 – Aug 23 |
| Winter Squash & Pumpkins | Apr 8 – Apr 15 | — | May 13 – May 27 | — |
| Melons & Watermelon | Apr 8 – Apr 15 | May 20 – Jun 3 | — | — |
| Carrots | — | — | Apr 15 – May 13 | Jul 26 – Aug 9 |
| Beets | — | — | Apr 15 – May 13 | Aug 9 – Aug 23 |
| Potatoes | — | — | Apr 15 – May 6 | — |
| Swiss Chard | — | — | Apr 22 – May 20 | Aug 9 – Aug 23 |
| Cilantro | — | — | Apr 22 – May 13 | Aug 23 – Sep 13 |
| Green Beans | — | — | May 13 – Jun 3 | Aug 2 – Aug 16 |
| Sweet Corn | — | — | May 13 – May 27 | — |
| Sweet Potatoes | — | May 20 – Jun 10 | — | — |
| Garlic | — | — | — | Oct 4 – Nov 8 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Dutch Harbor, AK weather station, 2 km away (elevation 10 ft (3 m)).
Frost dates near Unalaska
- Dutch Harbor May 6 · Oct 18
- Akutan May 6 · Oct 18
- False Pass May 25 · Oct 4
- Cold Bay May 25 · Oct 4
- King Cove May 25 · Oct 4
- Saint George Island May 31 · Oct 5
- Sand Point May 11 · Oct 18
- Saint Paul Island Jun 4 · Sep 28
- Perryville May 11 · Oct 18
- Chignik Lake May 11 · Oct 18
Frequently asked questions
When is the last frost in Unalaska, AK?
The median last spring frost in Unalaska, AK is May 6. There is still about a 10% chance of frost after May 22, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Unalaska, AK?
The median first fall frost is October 18, with about a 10% chance of frost before September 20.
How long is the growing season in Unalaska, AK?
About 165 days between the median last spring frost and first fall frost.
What planting zone is Unalaska, AK?
Unalaska, AK is in USDA hardiness zone 8a.