Napoleon, ND 58561 Frost Dates
Napoleon, ND: when does the frost end?
The last spring frost here typically falls around 05/13, about 258 days from today. Fall's first freeze usually shows up around 09/28, roughly 136 days after the last spring frost.
Napoleon sits in USDA Zone 4a (-30 to -25°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.
Stretching the season past the first frost
With roughly 4 weeks until Napoleon's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/13 isn't a guarantee
05/13 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/01 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/26 and only about 1 year in 10 sees frost after that.
Napoleon against the rest of the dataset
About 136 days separate Napoleon's last and first frost, putting it 37,740 of 40,283 ZIP codes nationally. Within ND, it ranks 230 of 405.
Learn more
Before leaning on 58561's figures: local microclimates explains what one yard in Napoleon can differ from the 58561 normal, while zone vs. frost date explains why Zone 4a and Napoleon's frost date answer different questions.