USDA zone 3b in Alaska
USDA plant hardiness zone 3b covers 12 locations across Alaska (average annual extreme minimum −35 to −30 °F): Akiachak, AK, Central, AK, Ester, AK, Ester, AK, Harding-Birch Lakes, AK, Healy, AK, and 6 more. Average last spring frost across this group ranges May 15 (Ester) to June 6 (Healy), and growing seasons run 75–122 days (Healy Lake to Ester) — 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 Willow, this group's median-season location.
- USDA zone
- 3b−35 to −30 °F
- Last frost range
- May 15–Jun 6avg, 32°F
- First frost range
- Aug 21–Sep 22avg, 32°F
- Growing season range
- 75–122days
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) |
|---|---|---|---|---|---|
| Akiachak | Russian Mission, Marshall, Upper Kalskag, Tuluksak, Akiak, Lower Kalskag | Bethel Ap | May 21 | Sep 22 | 122 |
| Central | — | Central #2 | May 25 | Aug 26 | 92 |
| Ester | — | Keystone Ridge | May 15 | Sep 16 | 122 |
| Ester | — | University Exp Stn | May 16 | Sep 8 | 114 |
| Harding-Birch Lakes | — | Eielson Fld | May 20 | Sep 1 | 104 |
| Healy | — | Mckinley Park | Jun 6 | Aug 25 | 77 |
| Healy Lake | — | Delta Junction 20 Se | Jun 5 | Aug 21 | 75 |
| Livengood | — | Gilmore Creek | Jun 1 | Aug 28 | 87 |
| Pleasant Valley | — | Two Rivers | May 30 | Sep 2 | 95 |
| St. Michael | Anvik, Koyuk, Unalakleet, Shaktoolik | Kaltag Ap | May 25 | Sep 3 | 101 |
| Stebbins | Nome, Wales, White Mountain | Nome Muni Ap | Jun 5 | Sep 3 | 88 |
| Willow * | — | Whites Crossing | May 29 | Sep 7 | 100 |
* Willow 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 (Willow, representative)
Computed from Willow's average frost dates — the median-season location in this Alaskazone 3b 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 3 – Apr 17 | Jun 5 – Jun 12 | Aug 4 – Aug 24 | — | matures comfortably |
| Pepper | Very tender | Mar 20 – Apr 3 | Jun 12 – Jun 19 | Aug 11 – Sep 10 | — | needs season extension (cold frame, row cover, or transplants) to mature |
| Cucumber | Tender | May 1 – May 8 | Jun 5 – Jun 12 | Jul 25 – Aug 14 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Jun 5 – Jun 12 | Jul 20 – Aug 4 | — | matures comfortably |
| Bush bean | Tender | — | Jun 5 – Jun 12 | Jul 25 – Aug 4 | Jul 9 – Jul 19 | matures comfortably |
| Sweet corn | Tender | — | May 29 – Jun 12 | Jul 28 – Aug 27 | — | matures, but with little margin |
| Basil | Very tender | Apr 17 – May 1 | Jun 5 – Jun 12 | Jul 5 – Jul 20 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 17 – May 1 | May 1 – May 15 | Jun 15 – Jun 30 | Jun 25 – Jul 10 | matures comfortably |
| Pea | Hardy | — | Apr 17 – May 1 | Jun 11 – Jun 26 | Jun 15 – Jun 30 | matures comfortably |
| Spinach | Hardy | — | Apr 17 – May 1 | May 27 – Jun 6 | Jul 5 – Jul 15 | matures comfortably |
| Carrot | Half-hardy | — | May 8 – May 15 | Jul 7 – Jul 27 | Jun 5 – Jun 25 | matures comfortably |
| Broccoli | Half-hardy | Apr 3 – Apr 17 | May 1 – May 15 | Jun 25 – Jul 15 | Jun 10 – Jun 30 | matures comfortably |
Which crops fit this growing season
Using Willow's own 100-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 10 of 12 crops mature here with comfortable margin, 1matures 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: pepper (-3 day margin), sweet corn (+11 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 (Willow)
From NOAA's 1991–2020 Climate Normals at station USC00509790. 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 | — | — | — | — | 74 |
| 32°F (freeze) | May 29 | Jun 9 | Sep 7 | Sep 21 | 100 |
| 28°F | May 14 | May 27 | Sep 19 | Oct 2 | 127 |
| 24°F | May 1 | May 17 | Sep 29 | Oct 15 | 150 |
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 12 locations is 774; Willow's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 794 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 2,168 | cool-season crops (brassicas, greens) |
Hardiness zone 3b in Alaska
Zone 3b means an average annual extreme minimum winter temperature of about −35 to −30 °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, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b.
Explore zone 3b in other states at zone 3b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 3b mean in Alaska?
- Zone 3b means an average annual extreme minimum winter temperature of −35 to −30 °F — the standard USDA measure of which perennials survive winter. 12 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 3b is the growing season longest?
- Ester runs the longest season on this page at about 122 days; Healy Lake is shortest at about 75 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 3b?
- Using Willow's frost dates (this page's median-season location): start seeds indoors about Apr 3 – Apr 17, then transplant outside about Jun 5 – Jun 12. 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 3b 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 12 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.