When Is the Last Frost in Alaska?
The average last spring frost in Alaska falls between May 1 and June 2 for most ZIP codes, with a statewide median of May 18. At the average date a later frost is still a coin flip, so tender plants wait for the safer 90% date.
| City | Last frost | 90% safe after | First frost | Growing season |
|---|---|---|---|---|
| Anchorage | May 16 | Jun 9 | Sep 20 | 125 days |
| Fairbanks | May 16 | May 29 | Sep 6 | 112 days |
| Juneau | May 3 | May 18 | Oct 14 | 164 days |
| Wasilla | May 16 | May 31 | Sep 23 | 128 days |
| Sitka | May 3 | May 19 | Oct 18 | 166 days |
| Ketchikan | Apr 14 | May 1 | Oct 25 | 192 days |
| Kenai | May 20 | Jun 1 | Sep 21 | 123 days |
| Palmer | May 22 | Jun 3 | Sep 16 | 114 days |
| Bethel | May 21 | Jun 2 | Sep 22 | 122 days |
| Homer | May 16 | May 30 | Sep 30 | 136 days |
| Kodiak | May 9 | May 23 | Oct 4 | 148 days |
| Unalaska | May 6 | May 22 | Oct 18 | 164 days |
| Valdez | Apr 30 | May 10 | Oct 2 | 157 days |
| Nome | Jun 5 | Jun 26 | Sep 3 | 88 days |
| Kotzebue | Jun 5 | Jun 17 | Sep 24 | 110 days |
| Seward | May 2 | May 17 | Oct 7 | 158 days |
| Cordova | Apr 30 | May 10 | Oct 2 | 157 days |
| Wrangell | Apr 11 | Apr 29 | Nov 1 | 202 days |
Last and first frost: 50% (median) dates of the last spring and first fall 32 °F night. 90% safe after: only a 10% chance of a later spring frost. First frost dates in January fall in the following winter. Each city uses the NOAA station nearest the ZIP code closest to its center.
Across all 163 Alaska weather stations with frost records, median last frost dates run from April 4 at Beaver Falls, AK to June 12 at Cooper Landing 5 W, AK. Elevation, valleys that collect cold air and distance from large water bodies explain most of the spread, so a garden a few miles from a listed city can differ by a week or more. The ZIP code lookup above uses the same NOAA data as the frost date calculator for every US ZIP code.
When Is the First Frost in Alaska?
The average first fall frost in Alaska arrives between August 28 and October 18 for most ZIP codes, with a median of September 22. Tomatoes, peppers, basil and squash are damaged at 32 °F, so harvest or cover them before then.
Fall frost can come early: Anchorage has a 10% chance of frost before September 4, Fairbanks has a 10% chance of frost before August 25 and Juneau has a 10% chance of frost before October 1. Hardy crops such as kale, spinach and cabbage tolerate light frosts and keep producing after the first frost date.
When to Plant Tomatoes in Alaska?
Transplant tomatoes in Alaska 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: May 23 – May 30 in Anchorage, May 23 – May 30 in Fairbanks and May 10 – May 17 in Juneau. Start seeds indoors 6 to 8 weeks before the last frost.
| City | Start seeds indoors | Transplant outdoors | Lowest-risk transplant |
|---|---|---|---|
| Anchorage | Mar 21 – Apr 4 | May 23 – May 30 | after Jun 9 |
| Fairbanks | Mar 21 – Apr 4 | May 23 – May 30 | after May 29 |
| Juneau | Mar 8 – Mar 22 | May 10 – May 17 | after May 18 |
| Wasilla | Mar 21 – Apr 4 | May 23 – May 30 | after May 31 |
| Sitka | Mar 8 – Mar 22 | May 10 – May 17 | after May 19 |
| Ketchikan | Feb 17 – Mar 3 | Apr 21 – Apr 28 | after May 1 |
| Kenai | Mar 25 – Apr 8 | May 27 – Jun 3 | after Jun 1 |
| Palmer | Mar 27 – Apr 10 | May 29 – Jun 5 | after Jun 3 |
| Bethel | Mar 26 – Apr 9 | May 28 – Jun 4 | after Jun 2 |
| Homer | Mar 21 – Apr 4 | May 23 – May 30 | after May 30 |
| Kodiak | Mar 14 – Mar 28 | May 16 – May 23 | after May 23 |
| Unalaska | Mar 11 – Mar 25 | May 13 – May 20 | after May 22 |
| Valdez | Mar 5 – Mar 19 | May 7 – May 14 | after May 10 |
| Nome | Apr 10 – Apr 24 | Jun 12 – Jun 19 | after Jun 26 |
| Kotzebue | Apr 10 – Apr 24 | Jun 12 – Jun 19 | after Jun 17 |
| Seward | Mar 7 – Mar 21 | May 9 – May 16 | after May 17 |
| Cordova | Mar 5 – Mar 19 | May 7 – May 14 | after May 10 |
| Wrangell | Feb 14 – Feb 28 | Apr 18 – Apr 25 | after Apr 29 |
Indoors: 6–8 weeks before the average last frost. Outdoors: 1–2 weeks after it. Lowest-risk: after the date with only a 10% chance of a later frost. Rules of thumb; check the 10-day forecast and wait for soil near 60 °F.
Tomatoes stall below about 50 °F at night and are killed by frost, so a week or two of waiting after the average date costs little. The tomato plant care guide covers light, watering and feeding once plants are in the ground. With a median growing season of only 122 days, early-maturing varieties, black plastic mulch or a greenhouse help tomatoes ripen before the first fall frost.
What Can You Plant in Anchorage and When?
Anchorage's average last frost of May 16 anchors its spring planting calendar: peas and spinach go in from April 4, broccoli and lettuce transplants from April 18, and tomatoes, peppers and squash after May 23.
| Crop | Start seeds indoors | Plant outdoors | Frost tolerance |
|---|---|---|---|
| Peas | — | Apr 4 – Apr 18direct sow, 4–6 weeks before last frost | hardy |
| Spinach | — | Apr 4 – Apr 25direct sow, 3–6 weeks before last frost | hardy |
| Radishes | — | Apr 11 – Apr 25direct sow, 3–5 weeks before last frost | hardy |
| Onions (sets) | — | Apr 18 – May 2plant, 2–4 weeks before last frost | hardy |
| Potatoes | — | Apr 18 – May 2plant, 2–4 weeks before last frost | half-hardy |
| Broccoli & cabbage | Mar 21 – Apr 4 | Apr 18 – May 2transplant, 2–4 weeks before last frost | hardy |
| Lettuce | Apr 4 – Apr 18 | Apr 18 – May 2transplant, 2–4 weeks before last frost | hardy |
| Beets | — | Apr 18 – May 2direct sow, 2–4 weeks before last frost | half-hardy |
| Carrots | — | Apr 25 – May 2direct sow, 2–3 weeks before last frost | half-hardy |
| Tomatoes | Mar 21 – Apr 4 | May 23 – May 30transplant, 1–2 weeks after last frost | tender |
| Basil | Mar 21 – Apr 4 | May 23 – Jun 6transplant, 1–3 weeks after last frost | tender |
| Peppers | Mar 7 – Mar 21 | May 30 – Jun 6transplant, 2–3 weeks after last frost | tender |
| Eggplant | Mar 7 – Mar 21 | May 30 – Jun 6transplant, 2–3 weeks after last frost | tender |
| Green beans | — | May 23 – Jun 6direct sow, 1–3 weeks after last frost | tender |
| Sweet corn | — | May 23 – Jun 6direct sow, 1–3 weeks after last frost | tender |
| Cucumbers | Apr 18 – Apr 25 | May 23 – Jun 6transplant, 1–3 weeks after last frost | tender |
| Squash & zucchini | Apr 18 – Apr 25 | May 23 – Jun 6transplant, 1–3 weeks after last frost | tender |
| Watermelon | Apr 18 – Apr 25 | May 30 – Jun 6transplant, 2–3 weeks after last frost | tender |
Dates for Anchorage (last frost May 16, NOAA station Eagle Rvr Nature Ctr, AK, 4 miles from ZIP 99577). General rules of thumb; wait for soil near 50 °F for most seeds and 60 °F for beans, corn and squash.
How Long Is the Growing Season in Alaska?
The frost-free growing season in Alaska lasts about 89 to 166 days for most ZIP codes, with a median of 122 days. Among the listed cities, Nome has the shortest season at 88 days and Wrangell the longest at 202.
Season length decides which varieties ripen: compare it with the “days to maturity” on seed packets, counted from transplanting for tomatoes and peppers. NOAA stations in Alaska range from 73 days at Gulkana AP, AK to 218 days at Beaver Falls, AK. Planning beds before the season starts helps in short seasons — a plant spacing calculator for vegetable beds shows how many transplants fit.
Frequently Asked Questions
- When is the last frost in Alaska?
- The average last spring frost in Alaska falls between May 1 and June 2 for most ZIP codes, with a statewide median of May 18. Among major cities it ranges from April 11 in Wrangell to June 5 in Kotzebue.
- When is the last frost in Anchorage, Alaska?
- Anchorage's average last spring frost is May 16, and by June 9 the chance of a later frost drops to 10%. Its first fall frost averages September 20, giving a 125-day growing season (NOAA station Eagle Rvr Nature Ctr, AK).
- When should you plant tomatoes in Alaska?
- Transplant tomatoes in Alaska 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: May 23 – May 30 in Anchorage, May 23 – May 30 in Fairbanks and May 10 – May 17 in Juneau. Start seeds indoors 6 to 8 weeks before the last frost.
- When is the first frost in Alaska?
- The average first fall frost in Alaska arrives between August 28 and October 18 for most ZIP codes, with a median of September 22. Harvest tender crops such as tomatoes, peppers and basil before then or cover them on cold nights.
- How long is the growing season in Alaska?
- The frost-free growing season in Alaska lasts about 89 to 166 days for most ZIP codes, with a median of 122 days, from 88 days in Nome to 202 days in Wrangell.
Frost data: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals (32 °F freeze dates by probability). ZIP code and city locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. Planting windows are general rules of thumb. PlantoScan is not affiliated with or endorsed by these agencies.