Sinai, SD 57061 Frost Dates
Frost dates for Sinai, SD, ZIP 57061
Around 05/03 is the usual last spring frost, about 248 days away. The first fall frost typically arrives around 10/02, about 151 frost-free days later.
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 Sinai, not a forecast for this year.
What to do before the first frost
Zone 4b around Sinai 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.
The actual range around Sinai's last frost
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/21 and you're betting against frost in roughly 9 years out of 10. 05/15 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Sinai compares
About 151 days separate Sinai's last and first frost, putting it 35,198 of 40,283 ZIP codes nationally. Within SD, it ranks 163 of 378.
Learn more
local microclimates explains what one yard in Sinai can differ from the 57061 normal, and zone vs. frost date explains why Zone 4b and Sinai's frost date answer different questions.