North Sioux City, SD 51109 Frost Dates
51109, near North Sioux City, SD: the frost window
Around 04/29 is the usual last spring frost, about 244 days away. Fall's first freeze usually shows up around 10/05, roughly 159 days after the last spring frost.
Zone 5a (-20 to -15°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 North Sioux City, not a forecast for this year.
Stretching the season past the first frost
North Sioux 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.
The actual range around North Sioux City's last frost
04/29 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/16 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/14 and only about 1 year in 10 sees frost after that.
North Sioux City against the rest of the dataset
At roughly 159 frost-free days, North Sioux City places 32,653 of 40,283 ZIP codes in this dataset. Within SD, it ranks 35 of 378.
Learn more
Two guides worth reading on 51109: local microclimates, on what one yard in North Sioux City can differ from the 51109 normal, and zone vs. frost date, on why Zone 5a and North Sioux City's frost date answer different questions.