Rapid City, SD 57709 Frost Dates
57709, near Rapid City, SD: the frost window
The last spring frost here typically falls around 05/10, about 255 days from today. Fall's first freeze usually shows up around 10/05, roughly 147 days after the last spring frost.
Zone 5b (-15 to -10°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 Rapid City, not a forecast for this year.
Stretching the season past the first frost
Rapid City'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.
How much risk comes with planting early here
05/10 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/27 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.
Rapid City against the rest of the dataset
At roughly 147 frost-free days, Rapid City places 35,830 of 40,283 ZIP codes in this dataset. Within SD, it ranks 210 of 378.
Learn more
Two guides worth reading on 57709: the frost range, on how to read the range around Rapid City's dates instead of trusting one, and local microclimates, on what one yard in Rapid City can differ from the 57709 normal.