Custer, SD 57730 Frost Dates
Custer, SD: when does the frost end?
Around 05/23 is the usual last spring frost, about 268 days away. Fall's first freeze usually shows up around 09/24, roughly 122 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 Custer, not a forecast for this year.
Stretching the season past the first frost
With roughly 4 weeks until Custer's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/23 isn't a guarantee
05/23 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/10 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.
Custer against the rest of the dataset
About 122 days separate Custer's last and first frost, putting it 38,947 of 40,283 ZIP codes nationally. Within SD, it ranks 372 of 378.
Learn more
Before leaning on 57730's figures: the frost range explains how to read the range around Custer's dates instead of trusting one, while local microclimates explains what one yard in Custer can differ from the 57730 normal.