Ronan, MT 59855 Frost Dates
Ronan, MT: when does the frost end?
The last spring frost here typically falls around 05/10, about 255 days from today. Fall's first freeze usually shows up around 10/05, roughly 147 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Ronan in Zone 6a (-10 to -5°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
With roughly 5 weeks until Ronan's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/10 isn't a guarantee
05/10 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/27 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.
Ronan against the rest of the dataset
About 147 days separate Ronan's last and first frost, putting it 35,914 of 40,283 ZIP codes nationally. Within MT, it ranks 31 of 392.
Learn more
Before leaning on 59855's figures: local microclimates explains what one yard in Ronan can differ from the 59855 normal, while zone vs. frost date explains why Zone 6a and Ronan's frost date answer different questions.