Anchorage, AK 99504 Frost Dates
99504, near Anchorage, AK: the frost window
The last spring frost here typically falls around 05/28, about 273 days from today. Fall's first freeze usually shows up around 09/12, roughly 107 days after the last spring frost.
Zone 5a (-20 to -15°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Anchorage, not a forecast for this year.
Stretching the season past the first frost
Anchorage's growing season runs out in roughly 2 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/28 isn't a guarantee
05/28 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/17 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/06 and only about 1 year in 10 sees frost after that.
Anchorage against the rest of the dataset
About 107 days separate Anchorage's last and first frost, putting it 39,555 of 40,283 ZIP codes nationally. Within AK, it ranks 179 of 269.
Learn more
Two guides worth reading on 99504: zone vs. frost date, on why Zone 5a and Anchorage's frost date answer different questions, and the frost range, on how to read the range around Anchorage's dates instead of trusting one.