Anchorage, Alaska: planting zone & frost dates
Anchorage is in USDA plant hardiness zone 5a, where the average coldest winter night reaches -20 to -15°F (-28.9 to -26.1°C). The typical last spring frost is around May 4 and the first fall frost around Sep 24.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 9 | Sep 17 |
| Typical planning date (30% risk) | May 4 | Sep 24 |
| Median (50%) | May 1 | Sep 29 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station ANCHORAGE MERRILL FLD, AK (USW00026409), 1.5 mi (2.4 km) from the city center and 33 ft higher than the city center (+10 m). Record used for the 1991–2020 normals: 23 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Anchorage
Anchorage spans more than one half-zone. Share of the city's land area by zone (via its 17 ZIP codes): 5a (68%), 5b (32%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Anchorage
Dates are counted from the 30%-risk frost dates above (last frost May 4, first frost Sep 24). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Pepper | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 23 – Apr 6 | Apr 20 – May 11 | Apr 6 – May 18 | Jul 16 – Aug 13 |
| Green Beans | — | — | May 11 – Jun 15 | Jul 2 – Jul 16 |
| Sweet Corn | — | — | May 11 – Jun 8 | — |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | May 11 – May 25 | May 11 – Jun 1 | Jul 2 – Jul 16 |
| Cucumber | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – Jun 1 | Jul 2 – Jul 16 |
| Carrot | — | — | Apr 13 – May 18 | Jul 2 – Jul 16 |
| Onion | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Potato | — | Apr 6 – Apr 27 | — | — |
| Basil | Mar 23 – Apr 6 | May 18 – Jun 1 | May 18 – Jun 8 | — |
| Spinach | — | — | Mar 23 – Apr 20 | Jul 30 – Aug 27 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 27 | Apr 6 – Apr 27 | Jul 16 – Aug 13 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 11 | — | Jul 2 – Jul 16 |
| Peas | — | — | Mar 23 – Apr 13 | Jul 16 – Jul 30 |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Cabbage | Mar 9 – Mar 23 | Apr 6 – Apr 20 | — | Jul 2 – Jul 16 |
| Radish | — | — | Mar 30 – May 18 | Aug 13 – Sep 10 |
| Strawberry | — | Apr 6 – Apr 27 | — | — |
| Beets | — | — | Apr 13 – May 25 | Jul 16 – Jul 30 |
Nearby cities in Alaska
- Fairbanks — zone 2a, last frost May 21, first frost Sep 1
More: all Alaska cities · other zone 5a cities: Minneapolis, MN, St. Paul, MN, Sioux Falls, SD, Cedar Rapids, IA, Billings, MT, Bloomington, MN, Sioux City, IA, Brooklyn Park, MN
Anchorage gardening questions
When is the last frost in Anchorage, AK?
Plan around May 4. At NOAA's Anchorage Merrill Field, AK station, 1.5 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by May 1, and after May 9 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 19. The last frost is fairly predictable here: only 20 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Anchorage, AK?
Start seeds indoors Mar 9 – Mar 23 and set transplants outside May 11 – May 25, once nights stay above 50°F and the soil is near 60°F. That leaves 143 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Anchorage?
About 150 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 135 days, and in 1 year in 10 it runs 167 days or more. In fall there is a 10% chance of frost by Sep 17 and a 30% chance by Sep 24.
When should I plant a fall garden in Anchorage?
Count back from the first fall frost (Sep 24): transplant broccoli Jul 2 – Jul 16; sow kale Jul 16 – Aug 13; sow lettuce Jul 16 – Aug 13; sow radishes Aug 13 – Sep 10. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 8. How the math works: succession and fall planting.
Did Anchorage's hardiness zone change on the 2023 map?
Yes. Most of Anchorage was zone 4b on the 2012 map and is zone 5a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Anchorage in zone 5a?
No. Zone 5a covers about 68% of the city's land; the rest is in 5b (32%), measured across the city's 17 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.