Eureka, MT 59917 Frost Dates
Eureka, MT: when does the frost end?
The last spring frost here typically falls around 05/11, about 256 days from today. Fall's first freeze usually shows up around 09/27, roughly 138 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Eureka 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 4 weeks until Eureka's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/11 isn't a guarantee
05/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/28 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/25 and only about 1 year in 10 sees frost after that.
Eureka against the rest of the dataset
At roughly 138 frost-free days, Eureka places 37,406 of 40,283 ZIP codes in this dataset. Within MT, it ranks 73 of 392.
Learn more
Before leaning on 59917's figures: zone vs. frost date explains why Zone 5a and Eureka's frost date answer different questions, while the frost range explains how to read the range around Eureka's dates instead of trusting one.