Portal, ND 58772 Frost Dates
58772, near Portal, ND: the frost window
Around 05/20 is the usual last spring frost, about 265 days away. Fall's first freeze usually shows up around 09/19, roughly 121 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Portal in Zone 3b (-35 to -30°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Portal's growing season runs out in roughly 3 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
05/20 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/09 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/02 and only about 1 year in 10 sees frost after that.
Portal against the rest of the dataset
About 121 days separate Portal's last and first frost, putting it 39,060 of 40,283 ZIP codes nationally. Within ND, it ranks 387 of 405.
Learn more
Two guides worth reading on 58772: local microclimates, on what one yard in Portal can differ from the 58772 normal, and zone vs. frost date, on why Zone 3b and Portal's frost date answer different questions.