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Frost Dates in Alaska
First and last frost dates across Alaska, computed from 74 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
May 13
statewide median · range Apr 4–Jun 7
First fall frost
Sep 27
statewide median · range Aug 21–Nov 9
Growing season
133 days
median · range 73–218
Stations used
74
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Anchorage | Anchorage Merrill Fld · 1 mi | May 1 (cautious: May 9) | Sep 29 | 150 days | May 15 |
| Fairbanks | College Obsy · 4 mi | May 18 (cautious: Jun 1) | Sep 6 | 111 days | Jun 1 |
| Juneau | Juneau Ap · 6 mi | May 4 (cautious: May 18) | Oct 3 | 150 days | May 18 |
How frost varies across Alaska
Spring frost timing spans about 64 days across the state. Beaver Falls in southeastern Alaska typically sees its last spring frost around April 4, while Puntilla in Alaska doesn't clear frost until about June 7. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Alaska
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 27 for the statewide median. Check your city's row above rather than the statewide median: a 64-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 74 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Alaska?
The statewide median last spring frost is May 13, but it ranges from April 4 to June 7 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Alaska?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 27 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Alaska?
The median growing season across 74 NOAA stations is 133 days, ranging from 73 to 218 days by location.
Why do frost dates vary so much within Alaska?
Frost timing follows latitude, elevation, and local terrain. Across Alaska, last spring frost dates span about 64 days — from around April 4 near Beaver Falls to June 7 near Puntilla. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.