Agar, SD 57520 Frost Dates
57520, near Agar, SD: the frost window
Typically, the last spring freeze lands around 05/14, roughly 259 days out. Fall's first freeze usually shows up around 09/29, roughly 138 days after the last spring frost.
Agar 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
Agar'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.
The actual range around Agar's last frost
05/14 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/30 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.
Agar against the rest of the dataset
Agar's growing season runs about 138 days, ranking 37,483 of 40,283 US ZIP codes measured here, longest to shortest. Within SD, it ranks 335 of 378.
Learn more
Two guides worth reading on 57520: local microclimates, on what one yard in Agar can differ from the 57520 normal, and zone vs. frost date, on why Zone 4b and Agar's frost date answer different questions.