Virgil, SD 57379 Frost Dates
57379, near Virgil, SD: the frost window
Typically, the last spring freeze lands around 05/06, roughly 251 days out. Fall's first freeze usually shows up around 10/02, roughly 146 days after the last spring frost.
Virgil sits in USDA Zone 4b (-25 to -20°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
Virgil's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/06 isn't a guarantee
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 05/20 and only about 1 year in 10 sees frost after that.
Virgil against the rest of the dataset
At roughly 146 frost-free days, Virgil places 36,155 of 40,283 ZIP codes in this dataset. Within SD, it ranks 227 of 378.
Learn more
Two guides worth reading on 57379: local microclimates, on what one yard in Virgil can differ from the 57379 normal, and zone vs. frost date, on why Zone 4b and Virgil's frost date answer different questions.