USDA zone 2a in Alaska
USDA plant hardiness zone 2a covers 14 locations across Alaska (average annual extreme minimum −50 to −45 °F): Alcan Border, AK, Ambler, AK, Anderson, AK, Anderson, AK, Atqasuk, AK, Badger, AK, and 8 more. Average last spring frost across this group ranges May 13 (Takotna) to June 10 (Atqasuk), and growing seasons run 77–122 days (Healy to Minto) — 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 Ambler, this group's median-season location.
- USDA zone
- 2a−50 to −45 °F
- Last frost range
- May 13–Jun 10avg, 32°F
- First frost range
- Aug 24–Sep 24avg, 32°F
- Growing season range
- 77–122days
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) |
|---|---|---|---|---|---|
| Alcan Border | Chicken | Northway Ap | May 26 | Sep 1 | 97 |
| Ambler * | Selawik, Kiana | Kotzebue Ralph Wein Ap | Jun 5 | Sep 24 | 110 |
| Anderson | — | Clear Sky | May 24 | Sep 4 | 100 |
| Anderson | — | Nenana Muni Ap | May 15 | Sep 11 | 117 |
| Atqasuk | Noatak | Kivalina Ap | Jun 10 | Sep 11 | 92 |
| Badger | — | N Pole | May 18 | Sep 5 | 110 |
| Eielson AFB | — | Eielson Fld | May 20 | Sep 1 | 104 |
| Fairbanks | — | College Obsy | May 18 | Sep 6 | 111 |
| Healy | — | Mckinley Park | Jun 6 | Aug 25 | 77 |
| Huslia | Koyukuk | Galena | May 18 | Sep 8 | 111 |
| Minto | — | Keystone Ridge | May 15 | Sep 16 | 122 |
| Nulato | Kaltag | Kaltag Ap | May 25 | Sep 3 | 101 |
| Prudhoe Bay | Nuiqsut | Bettles Ap | May 22 | Aug 24 | 94 |
| Takotna | — | Mcgrath Ap | May 13 | Sep 13 | 120 |
* Ambler 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 (Ambler, representative)
Computed from Ambler's average frost dates — the median-season location in this Alaskazone 2a 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 | Apr 10 – Apr 24 | Jun 12 – Jun 19 | Aug 11 – Aug 31 | — | matures comfortably |
| Pepper | Very tender | Mar 27 – Apr 10 | Jun 19 – Jun 26 | Aug 18 – Sep 17 | — | matures, but with little margin |
| Cucumber | Tender | May 8 – May 15 | Jun 12 – Jun 19 | Aug 1 – Aug 21 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Jun 12 – Jun 19 | Jul 27 – Aug 11 | — | matures comfortably |
| Bush bean | Tender | — | Jun 12 – Jun 19 | Aug 1 – Aug 11 | Jul 26 – Aug 5 | matures comfortably |
| Sweet corn | Tender | — | Jun 5 – Jun 19 | Aug 4 – Sep 3 | — | matures comfortably |
| Basil | Very tender | Apr 24 – May 8 | Jun 12 – Jun 19 | Jul 12 – Jul 27 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 24 – May 8 | May 8 – May 22 | Jun 22 – Jul 7 | Jul 12 – Jul 27 | matures comfortably |
| Pea | Hardy | — | Apr 24 – May 8 | Jun 18 – Jul 3 | Jul 2 – Jul 17 | matures comfortably |
| Spinach | Hardy | — | Apr 24 – May 8 | Jun 3 – Jun 13 | Jul 22 – Aug 1 | matures comfortably |
| Carrot | Half-hardy | — | May 15 – May 22 | Jul 14 – Aug 3 | Jun 22 – Jul 12 | matures comfortably |
| Broccoli | Half-hardy | Apr 10 – Apr 24 | May 8 – May 22 | Jul 2 – Jul 22 | Jun 27 – Jul 17 | matures comfortably |
Which crops fit this growing season
Using Ambler's own 110-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 11 of 12 crops mature here with comfortable margin, 1matures with little room to spare. The tightest fits: pepper (+7 day 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 (Ambler)
From NOAA's 1991–2020 Climate Normals at station USW00026616. 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 | Jun 15 | Jul 1 | Sep 12 | Sep 25 | 87 |
| 32°F (freeze) | Jun 5 | Jun 17 | Sep 24 | Oct 6 | 110 |
| 28°F | May 27 | Jun 7 | Oct 3 | Oct 15 | 128 |
| 24°F | May 16 | May 30 | Oct 11 | Oct 21 | 145 |
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 14 locations is 799; Ambler's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 372 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 1,273 | cool-season crops (brassicas, greens) |
Hardiness zone 2a in Alaska
Zone 2a means an average annual extreme minimum winter temperature of about −50 to −45 °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, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b.
Explore zone 2a in other states at zone 2a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 2a mean in Alaska?
- Zone 2a means an average annual extreme minimum winter temperature of −50 to −45 °F — the standard USDA measure of which perennials survive winter. 14 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 2a is the growing season longest?
- Minto runs the longest season on this page at about 122 days; Healy is shortest at about 77 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 2a?
- Using Ambler's frost dates (this page's median-season location): start seeds indoors about Apr 10 – Apr 24, then transplant outside about Jun 12 – Jun 19. 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 2a 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 14 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.