Frederick, SD 57441 Frost Dates
57441, near Frederick, SD: the frost window
The last spring frost here typically falls around 05/09, about 254 days from today. Fall's first freeze usually shows up around 09/28, roughly 141 days after the last spring frost.
Zone 4b (-25 to -20°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 Frederick, not a forecast for this year.
Stretching the season past the first frost
Frederick's growing season runs out in roughly 4 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 Frederick's last frost
05/09 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/28 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/21 and only about 1 year in 10 sees frost after that.
Frederick against the rest of the dataset
At roughly 141 frost-free days, Frederick places 36,996 of 40,283 ZIP codes in this dataset. Within SD, it ranks 303 of 378.
Learn more
Two guides worth reading on 57441: zone vs. frost date, on why Zone 4b and Frederick's frost date answer different questions, and the frost range, on how to read the range around Frederick's dates instead of trusting one.