Unalaska, AK 99638 Frost Dates
Unalaska, AK: when does the frost end?
Around 05/06 is the usual last spring frost, about 251 days away. Fall's first freeze usually shows up around 10/18, roughly 164 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Unalaska in Zone 8b (15 to 20°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 7 weeks until Unalaska's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
05/06 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/23 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/22 and only about 1 year in 10 sees frost after that.
Unalaska against the rest of the dataset
About 164 days separate Unalaska's last and first frost, putting it 30,918 of 40,283 ZIP codes nationally. Within AK, it ranks 25 of 269.
Learn more
Before leaning on 99638's figures: local microclimates explains what one yard in Unalaska can differ from the 99638 normal, while zone vs. frost date explains why Zone 8b and Unalaska's frost date answer different questions.