Anchorage, AK 99540 Frost Dates
99540, near Anchorage, AK: the frost window
Typically, the last spring freeze lands around 05/18, roughly 263 days out. Fall's first freeze usually shows up around 09/24, roughly 127 days after the last spring frost.
Zone 5b (-15 to -10°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 4 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Anchorage's last frost
05/18 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/08 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/28 and only about 1 year in 10 sees frost after that.
Anchorage against the rest of the dataset
At roughly 127 frost-free days, Anchorage places 38,603 of 40,283 ZIP codes in this dataset. Within AK, it ranks 84 of 269.
Learn more
Two guides worth reading on 99540: local microclimates, on what one yard in Anchorage can differ from the 99540 normal, and zone vs. frost date, on why Zone 5b and Anchorage's frost date answer different questions.