Anchorage, AK Frost Dates: Last Spring and First Fall Frost

The last spring frost in Anchorage, AK comes on May 21 in a typical year, and the first fall frost follows on September 15, leaving a frost-free season of 116 days.

Put June 3 and August 31 on the calendar as well. A spring freeze after the first of them, or a fall freeze before the second, happens in only one year out of ten, so those dates cover nine years in ten. Among the 100 cities covered here, whose median season is 229 days, Anchorage ranks 100th for length and falls 113 days below the middle.

Behind every date on this page is one weather station, Eagle River 5 SE (NOAA USC00502656), 9.9 miles north-west of Anchorage's internal point in the Census Bureau's files and about 500 feet up.

When is the last frost in Anchorage?

One year in ten has a freeze on or after June 3. In nine years out of ten there is still a freeze on or after May 8, and half of years see one on or after May 21.

The early and late dates sit just 26 days apart, narrower than for most cities on these pages. Spring in Anchorage rarely surprises by much.

When is the first frost in Anchorage?

NOAA's early fall date for Anchorage is August 31, its even-odds date is September 15 and its late date is September 27; the first freeze has come by each of them in one, five and nine years out of ten.

The early and late fall dates are only 27 days apart, a narrow band next to most cities here, so the first freeze keeps close to its schedule in Anchorage.

How long is the frost-free season in Anchorage?

With a season well short of the middle of these pages, Anchorage leaves little time for slow crops, as the planting dates below show. A short year costs just 20 days against a typical one (96 days against 116 days), so a season-length plan for Anchorage holds up in most years.

The season lengths come from NOAA's simulated years, not from subtracting one typical date from the other, so the two will not match to the day. A night at or below 32°F happens in 100% of years at this station, so frost is a yearly event here.

28°F dates in Anchorage

Light frost and hard freeze are well separated in Anchorage. In fall the typical 28°F night comes on September 26, 11 days after the first 32°F frost on September 15; in spring the last one comes on May 5, 16 days before the last 32°F frost. Crops that tolerate light frost have that stretch to themselves. The late 28°F spring date, May 19, is the one that still catches blooms and young transplants one year in ten, and the early fall date, September 10, is when a hard freeze has arrived in one fall out of ten.

What this means for planting in Anchorage

University of New Hampshire Extension sorts vegetables by how they cope with cold. Cool-season crops go out before the last frost: counting from May 21, cabbage transplants go in on April 23 and lettuce from April 23 to April 30. Tender crops wait until it has passed, with peppers going out on June 4 and beans sown on or after May 21. The University of New Hampshire Extension sheet gives peas no frost count at all; sow them as soon as the soil thaws.

The late date comes 13 days after the typical one; choose it for plants you cannot cover.

Of the 34 crops in the fall planner, 7 still have a July-or-later last planting day in Anchorage once NC State Extension's days to harvest and University of Georgia Extension's harvest allowance of 18 days are counted back from frost. The other 27 do not. Of the crops that fit, Swiss chard is the slowest: 60 days from planting to the early frost, which makes July 2 its last day.

Worked example: tomatoes in Anchorage

Suppose you want tomatoes in Anchorage. University of New Hampshire Extension says to set transplants out one to two weeks after the last frost. Counting from the typical date, May 21, the window runs from May 28 to June 4. Counting from the late date, June 3, it moves to June 10 through June 17, which is 13 days later.

Seeds start six to eight weeks before the set-out day, so counting back from the first day of the late window gives April 15 to April 29 for sowing indoors.

The arithmetic is tight in Anchorage: 75 days between the last set-out day and the early first frost on August 31, against up to 85 days needed, a shortfall of 10 days in the worst case.

Where Anchorage's numbers are measured

At 9.9 miles north-west, the station is some distance from Anchorage, so parts of the city may not match its record.

Its elevation is about 500 feet. Of the 100 stations behind these pages, 63 sit higher and 36 lower. NOAA flags this station's record as standard, the code S, for the data behind its 50% last-frost value.

No elevation is available for Anchorage in the Census data we saved, so the station's height may or may not match your garden's. Compare nearby stations in the frost dates tool if it does not, and err toward the colder dates.

Anchorage compared with nearby cities

The closest city to Anchorage on these pages, Seattle, WA, is 1,414 miles away, a long way, so the three below are a look at other climates more than at neighbors.

• Seattle, WA, 1,414 miles to the south-east: last frost March 8, first frost November 23, 259 days frost-free; the last frost is 74 days earlier than in Anchorage, and it has 143 days more without frost.
• Tacoma, WA (1,431 miles, south-east): spring frost ends 74 days sooner than in Anchorage, and it has 134 days more without frost. Its typical dates are March 8 and November 14, with 250 days frost-free.
• Portland, OR lies 1,520 miles south-east of Anchorage. Typical last frost February 25, first frost December 1, 280 days between; spring frost ends 85 days sooner than in Anchorage, and the season runs 164 days longer.

Take these dates further

Open the frost dates tool with this station already chosen to see the whole ladder of probability dates, or try the nearby stations in the same list. The spring planting planner and the fall planting planner turn the same dates into a full crop list, and the hardiness zone lookup tells you which perennials will survive the winter.

Looking for another city? The city frost dates index lists every page, grouped by state.

Where these numbers come from

Every frost and freeze date comes from the station's entry in NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), with no adjustment, and NOAA's documentation explains what each probability means. The city and its internal point come from the Census Bureau's 2024 Gazetteer of places, and the ranking by size from the Census Bureau's Vintage 2024 city and town population estimates, which put Anchorage at 289,600 people.

The planting dates apply the count rules in University of New Hampshire Extension, NC State Extension and University of Georgia Extension to this station's dates, with nothing added. The methodology page explains how each figure is checked.

NOAA's dates say how often frost has come, not when it will. Check the forecast before planting and keep a cover on hand.