Neihart, MT 59465 Frost Dates
59465, near Neihart, MT: the frost window
The last spring frost here typically falls around 06/06, about 282 days from today. Fall's first freeze usually shows up around 09/12, roughly 99 days after the last spring frost.
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 Neihart, not a forecast for this year.
Stretching the season past the first frost
Neihart's growing season runs out in roughly 2 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 06/06 isn't a guarantee
06/06 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/23 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/28 and only about 1 year in 10 sees frost after that.
Neihart against the rest of the dataset
Neihart's growing season runs about 99 days, ranking 39,745 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 318 of 392.
Learn more
Two guides worth reading on 59465: zone vs. frost date, on why Zone 4b and Neihart's frost date answer different questions, and the frost range, on how to read the range around Neihart's dates instead of trusting one.