Cascade, MT 59620 Frost Dates
Cascade, MT: when does the frost end?
Around 05/21 is the usual last spring frost, about 266 days away. Fall's first freeze usually shows up around 09/15, roughly 115 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Cascade in Zone 5a (-20 to -15°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 3 weeks until Cascade'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
05/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/08 and only about 1 year in 10 sees frost after that.
Cascade against the rest of the dataset
Cascade's growing season runs about 115 days, ranking 39,334 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 250 of 392.
Learn more
Before leaning on 59620's figures: the frost range explains how to read the range around Cascade's dates instead of trusting one, while local microclimates explains what one yard in Cascade can differ from the 59620 normal.