De Smet, SD 57231 Frost Dates
Frost dates for De Smet, SD, ZIP 57231
Typically, the last spring freeze lands around 05/05, roughly 250 days out. The first fall frost typically arrives around 10/04, about 151 frost-free days later.
De Smet 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.
What to do before the first frost
Zone 4b around De Smet has about 5 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
How much risk comes with planting early here
05/05 is the middle of 30 years of NOAA records, not a promise. Plant by 04/22 and you're betting against frost in roughly 9 years out of 10. 05/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How De Smet compares
De Smet's growing season runs about 151 days, ranking 35,093 of 40,283 US ZIP codes measured here, longest to shortest. Within SD, it ranks 146 of 378.
Learn more
local microclimates explains what one yard in De Smet can differ from the 57231 normal, and zone vs. frost date explains why Zone 4b and De Smet's frost date answer different questions.