Ortley, SD 57256 Frost Dates
57256, near Ortley, SD: the frost window
Around 05/14 is the usual last spring frost, about 259 days away. Fall's first freeze usually shows up around 09/28, roughly 136 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Ortley in Zone 4b (-25 to -20°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
Ortley'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.
Why 05/14 isn't a guarantee
05/14 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/01 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/28 and only about 1 year in 10 sees frost after that.
Ortley against the rest of the dataset
At roughly 136 frost-free days, Ortley places 37,819 of 40,283 ZIP codes in this dataset. Within SD, it ranks 351 of 378.
Learn more
Two guides worth reading on 57256: the frost range, on how to read the range around Ortley's dates instead of trusting one, and local microclimates, on what one yard in Ortley can differ from the 57256 normal.