USDA zone 8a in Alaska
USDA plant hardiness zone 8a covers 7 locations across Alaska (average annual extreme minimum 10 to 15 °F): Coffman Cove, AK, Hydaburg, AK, Metlakatla, AK, Port Alexander, AK, Port Protection, AK, Tatitlek, AK, and 1 more. Average last spring frost across this group ranges April 4 (Metlakatla) to May 6 (Unalaska), and growing seasons run 157–208 days (Tatitlek to Metlakatla) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Alaska location's own frost dates; the printable planting calendar uses Port Protection, this group's median-season location.
- USDA zone
- 8a10 to 15 °F
- Last frost range
- Apr 4–May 6avg, 32°F
- First frost range
- Oct 2–Nov 5avg, 32°F
- Growing season range
- 157–208days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Coffman Cove | — | Klawock Ap | Apr 29 | Oct 16 | 169 |
| Hydaburg | — | Craig | Apr 14 | Nov 1 | 201 |
| Metlakatla | — | Annette Island Ap | Apr 4 | Oct 31 | 208 |
| Port Alexander | — | Port Alexander | Apr 18 | Nov 5 | 198 |
| Port Protection * | — | Pt Baker | Apr 19 | Oct 25 | 187 |
| Tatitlek | — | Valdez Wso | Apr 30 | Oct 2 | 157 |
| Unalaska | Akutan | Dutch Harbor | May 6 | Oct 18 | 164 |
* Port Protection is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Port Protection, representative)
Computed from Port Protection's average frost dates — the median-season location in this Alaskazone 8a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Feb 22 – Mar 8 | Apr 26 – May 3 | Jun 25 – Jul 15 | — | matures comfortably |
| Pepper | Very tender | Feb 8 – Feb 22 | May 3 – May 10 | Jul 2 – Aug 1 | — | matures comfortably |
| Cucumber | Tender | Mar 22 – Mar 29 | Apr 26 – May 3 | Jun 15 – Jul 5 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Apr 26 – May 3 | Jun 10 – Jun 25 | — | matures comfortably |
| Bush bean | Tender | — | Apr 26 – May 3 | Jun 15 – Jun 25 | Aug 26 – Sep 5 | matures comfortably |
| Sweet corn | Tender | — | Apr 19 – May 3 | Jun 18 – Jul 18 | — | matures comfortably |
| Basil | Very tender | Mar 8 – Mar 22 | Apr 26 – May 3 | May 26 – Jun 10 | — | matures comfortably |
| Lettuce | Half-hardy | Mar 8 – Mar 22 | Mar 22 – Apr 5 | May 6 – May 21 | Aug 12 – Aug 27 | matures comfortably |
| Pea | Hardy | — | Mar 8 – Mar 22 | May 2 – May 17 | Aug 2 – Aug 17 | matures comfortably |
| Spinach | Hardy | — | Mar 8 – Mar 22 | Apr 17 – Apr 27 | Aug 22 – Sep 1 | matures comfortably |
| Carrot | Half-hardy | — | Mar 29 – Apr 5 | May 28 – Jun 17 | Jul 23 – Aug 12 | matures comfortably |
| Broccoli | Half-hardy | Feb 22 – Mar 8 | Mar 22 – Apr 5 | May 16 – Jun 5 | Jul 28 – Aug 17 | matures comfortably |
Which crops fit this growing season
Using Port Protection's own 187-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Port Protection)
From NOAA's 1991–2020 Climate Normals at station USC00507421. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 9 | May 25 | Oct 10 | Oct 24 | 153 |
| 32°F (freeze) | Apr 19 | May 5 | Oct 25 | Nov 11 | 187 |
| 28°F | Apr 3 | Apr 22 | Nov 8 | Dec 2 | 219 |
| 24°F | Mar 23 | Apr 12 | Nov 26 | Dec 30 | 251 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 7 locations is 617; Port Protection's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 442 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 2,133 | cool-season crops (brassicas, greens) |
Hardiness zone 8a in Alaska
Zone 8a means an average annual extreme minimum winter temperature of about 10 to 15 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Alaska spans 16 hardiness zones in this dataset — see all Alaska locations for the full range, including zones1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8b.
Explore zone 8a in other states at zone 8a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 8a mean in Alaska?
- Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 7 locations in Alaska fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Alaska's zone 8a is the growing season longest?
- Metlakatla runs the longest season on this page at about 208 days; Tatitlek is shortest at about 157 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Alaska's zone 8a?
- Using Port Protection's frost dates (this page's median-season location): start seeds indoors about Feb 22 – Mar 8, then transplant outside about Apr 26 – May 3. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Alaska's zone 8a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 7 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.