USDA zone 3a in Alaska
USDA plant hardiness zone 3a covers 11 locations across Alaska (average annual extreme minimum −40 to −35 °F): Arctic, AK, Brevig Mission, AK, Coldfoot, AK, Crooked Creek, AK, Deering, AK, Dry Creek, AK, and 5 more. Average last spring frost across this group ranges May 12 (Lime) to June 10 (Point Hope), and growing seasons run 84–134 days (Dry Creek to Lime) — 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 Coldfoot, this group's median-season location.
- USDA zone
- 3a−40 to −35 °F
- Last frost range
- May 12–Jun 10avg, 32°F
- First frost range
- Aug 24–Sep 24avg, 32°F
- Growing season range
- 84–134days
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) |
|---|---|---|---|---|---|
| Arctic | Kaktovik | Central #2 | May 25 | Aug 26 | 92 |
| Brevig Mission | Shishmaref, Teller | Nome Muni Ap | Jun 5 | Sep 3 | 88 |
| Coldfoot * | — | Bettles Ap | May 22 | Aug 24 | 94 |
| Crooked Creek | Red Devil | Mcgrath Ap | May 13 | Sep 13 | 120 |
| Deering | — | Kotzebue Ralph Wein Ap | Jun 5 | Sep 24 | 110 |
| Dry Creek | — | Dry Creek | May 30 | Aug 24 | 84 |
| Grayling | Shageluk | Kaltag Ap | May 25 | Sep 3 | 101 |
| Holy Cross | — | Bethel Ap | May 21 | Sep 22 | 122 |
| Lime | — | Port Alsworth | May 12 | Sep 24 | 134 |
| Point Hope | Kivalina | Kivalina Ap | Jun 10 | Sep 11 | 92 |
| Tanana | — | Tanana Calhoun Mem Ap | May 29 | Aug 28 | 89 |
* Coldfoot 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 (Coldfoot, representative)
Computed from Coldfoot's average frost dates — the median-season location in this Alaskazone 3a 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 | Mar 27 – Apr 10 | May 29 – Jun 5 | Jul 28 – Aug 17 | — | matures, but with little margin |
| Pepper | Very tender | Mar 13 – Mar 27 | Jun 5 – Jun 12 | Aug 4 – Sep 3 | — | needs season extension (cold frame, row cover, or transplants) to mature |
| Cucumber | Tender | Apr 24 – May 1 | May 29 – Jun 5 | Jul 18 – Aug 7 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 29 – Jun 5 | Jul 13 – Jul 28 | — | matures comfortably |
| Bush bean | Tender | — | May 29 – Jun 5 | Jul 18 – Jul 28 | Jun 25 – Jul 5 | matures comfortably |
| Sweet corn | Tender | — | May 22 – Jun 5 | Jul 21 – Aug 20 | — | matures, but with little margin |
| Basil | Very tender | Apr 10 – Apr 24 | May 29 – Jun 5 | Jun 28 – Jul 13 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 10 – Apr 24 | Apr 24 – May 8 | Jun 8 – Jun 23 | Jun 11 – Jun 26 | matures comfortably |
| Pea | Hardy | — | Apr 10 – Apr 24 | Jun 4 – Jun 19 | Jun 1 – Jun 16 | matures comfortably |
| Spinach | Hardy | — | Apr 10 – Apr 24 | May 20 – May 30 | Jun 21 – Jul 1 | matures comfortably |
| Carrot | Half-hardy | — | May 1 – May 8 | Jun 30 – Jul 20 | May 22 – Jun 11 | matures comfortably |
| Broccoli | Half-hardy | Mar 27 – Apr 10 | Apr 24 – May 8 | Jun 18 – Jul 8 | May 27 – Jun 16 | matures comfortably |
Which crops fit this growing season
Using Coldfoot's own 94-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 9 of 12 crops mature here with comfortable margin, 2mature with little room to spare, and 1 needs season extension (starting indoors earlier, a cold frame, or row cover) to reliably reach harvest before the first fall frost. The tightest fits: tomato (+7 day margin), pepper (-10 day margin), sweet corn (+4 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 (Coldfoot)
From NOAA's 1991–2020 Climate Normals at station USW00026533. 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 | — | — | — | — | 67 |
| 32°F (freeze) | May 22 | Jun 5 | Aug 24 | Sep 9 | 94 |
| 28°F | May 13 | May 28 | Sep 5 | Sep 25 | 115 |
| 24°F | May 7 | May 22 | Sep 19 | Oct 4 | 133 |
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 11 locations is 747; Coldfoot's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 754 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 1,904 | cool-season crops (brassicas, greens) |
Hardiness zone 3a in Alaska
Zone 3a means an average annual extreme minimum winter temperature of about −40 to −35 °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, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b.
Explore zone 3a in other states at zone 3a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 3a mean in Alaska?
- Zone 3a means an average annual extreme minimum winter temperature of −40 to −35 °F — the standard USDA measure of which perennials survive winter. 11 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 3a is the growing season longest?
- Lime runs the longest season on this page at about 134 days; Dry Creek is shortest at about 84 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 3a?
- Using Coldfoot's frost dates (this page's median-season location): start seeds indoors about Mar 27 – Apr 10, then transplant outside about May 29 – Jun 5. 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 3a 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 11 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.