Knox, ND 58343 Frost Dates
58343, near Knox, ND: the frost window
Around 05/11 is the usual last spring frost, about 256 days away. Fall's first freeze usually shows up around 09/28, roughly 138 days after the last spring frost.
Zone 4a (-30 to -25°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 Knox, not a forecast for this year.
Stretching the season past the first frost
Knox'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.
The actual range around Knox's last frost
05/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/23 and only about 1 year in 10 sees frost after that.
Knox against the rest of the dataset
Knox's growing season runs about 138 days, ranking 37,493 of 40,283 US ZIP codes measured here, longest to shortest. Within ND, it ranks 209 of 405.
Learn more
Two guides worth reading on 58343: local microclimates, on what one yard in Knox can differ from the 58343 normal, and zone vs. frost date, on why Zone 4a and Knox's frost date answer different questions.