Sunburst, MT 59466 Frost Dates
59466, near Sunburst, MT: the frost window
Around 05/17 is the usual last spring frost, about 262 days away. Fall's first freeze usually shows up around 09/25, roughly 129 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
05/17 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/02 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/31 and only about 1 year in 10 sees frost after that.
Sunburst against the rest of the dataset
About 129 days separate Sunburst's last and first frost, putting it 38,502 of 40,283 ZIP codes nationally. Within MT, it ranks 144 of 392.
Learn more
Two guides worth reading on 59466: the frost range, on how to read the range around Sunburst's dates instead of trusting one, and local microclimates, on what one yard in Sunburst can differ from the 59466 normal.