Spearfish, SD 57779 Frost Dates
Spearfish, SD: when does the frost end?
Around 05/12 is the usual last spring frost, about 257 days away. Fall's first freeze usually shows up around 10/02, roughly 143 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Spearfish in Zone 5b (-15 to -10°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 5 weeks until Spearfish's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/12 isn't a guarantee
05/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/25 and only about 1 year in 10 sees frost after that.
Spearfish against the rest of the dataset
At roughly 143 frost-free days, Spearfish places 36,502 of 40,283 ZIP codes in this dataset. Within SD, it ranks 265 of 378.
Learn more
Before leaning on 57779's figures: the frost range explains how to read the range around Spearfish's dates instead of trusting one, while local microclimates explains what one yard in Spearfish can differ from the 57779 normal.