Eureka, MT 59918 Frost Dates
Frost dates for Eureka, MT, ZIP 59918
The last spring frost here typically falls around 05/16, about 261 days from today. The first fall frost typically arrives around 09/18, about 121 frost-free days later.
Eureka sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 5a around Eureka has about 3 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
The actual range around Eureka's last frost
05/16 is the middle of 30 years of NOAA records, not a promise. Plant by 05/03 and you're betting against frost in roughly 9 years out of 10. 06/03 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Eureka compares
At roughly 121 frost-free days, Eureka places 39,017 of 40,283 ZIP codes in this dataset. Within MT, it ranks 206 of 392.
Learn more
zone vs. frost date explains why Zone 5a and Eureka's frost date answer different questions, and the frost range explains how to read the range around Eureka's dates instead of trusting one.