Billings, MT 59117 Frost Dates
Frost dates for Billings, MT, ZIP 59117
Typically, the last spring freeze lands around 05/12, roughly 257 days out. The first fall frost typically arrives around 09/25, about 136 frost-free days later.
The USDA Plant Hardiness Zone Map puts Billings in Zone 5a (-20 to -15°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 5a around Billings has about 4 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.
How much risk comes with planting early here
05/12 is the middle of 30 years of NOAA records, not a promise. Plant by 04/30 and you're betting against frost in roughly 9 years out of 10. 05/26 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Billings compares
About 136 days separate Billings's last and first frost, putting it 37,621 of 40,283 ZIP codes nationally. Within MT, it ranks 92 of 392.
Learn more
local microclimates explains what one yard in Billings can differ from the 59117 normal, and zone vs. frost date explains why Zone 5a and Billings's frost date answer different questions.