Eureka, MT 59934 Frost Dates
When can you plant in Eureka, MT?
Typically, the last spring freeze lands around 05/16, roughly 261 days out. 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
About 3 weeks of growing season left in Eureka before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
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
About 121 days separate Eureka's last and first frost, putting it 39,019 of 40,283 ZIP codes nationally. Within MT, it ranks 208 of 392.
Learn more
local microclimates covers what one yard in Eureka can differ from the 59934 normal. zone vs. frost date covers why Zone 5a and Eureka's frost date answer different questions.