Libby, MT 59923 Frost Dates
Libby, MT: when does the frost end?
Around 05/11 is the usual last spring frost, about 256 days away. Fall's first freeze usually shows up around 10/01, roughly 142 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Libby 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 Libby's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
05/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/27 and only about 1 year in 10 sees frost after that.
Libby against the rest of the dataset
About 142 days separate Libby's last and first frost, putting it 36,736 of 40,283 ZIP codes nationally. Within MT, it ranks 54 of 392.
Learn more
Before leaning on 59923's figures: zone vs. frost date explains why Zone 6a and Libby's frost date answer different questions, while the frost range explains how to read the range around Libby's dates instead of trusting one.