Ennis, MT 59720 Frost Dates
59720, near Ennis, MT: the frost window
Around 06/15 is the usual last spring frost, about 291 days away. Fall's first freeze usually shows up around 09/10, roughly 87 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Ennis 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
Ennis's growing season runs out in roughly 2 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
06/15 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 07/07 and only about 1 year in 10 sees frost after that.
Ennis against the rest of the dataset
About 87 days separate Ennis's last and first frost, putting it 39,965 of 40,283 ZIP codes nationally. Within MT, it ranks 347 of 392.
Learn more
Two guides worth reading on 59720: zone vs. frost date, on why Zone 5a and Ennis's frost date answer different questions, and the frost range, on how to read the range around Ennis's dates instead of trusting one.