Sunburst, MT 59484 Frost Dates
59484, near Sunburst, MT: the frost window
The last spring frost here typically falls around 05/15, about 260 days from today. Fall's first freeze usually shows up around 09/25, roughly 132 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Sunburst in Zone 4a (-30 to -25°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
Sunburst'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.
How much risk comes with planting early here
05/15 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/03 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/28 and only about 1 year in 10 sees frost after that.
Sunburst against the rest of the dataset
At roughly 132 frost-free days, Sunburst places 38,223 of 40,283 ZIP codes in this dataset. Within MT, it ranks 125 of 392.
Learn more
Two guides worth reading on 59484: zone vs. frost date, on why Zone 4a and Sunburst's frost date answer different questions, and the frost range, on how to read the range around Sunburst's dates instead of trusting one.