Big Timber, MT 59061 Frost Dates
Frost dates for Big Timber, MT, ZIP 59061
Around 06/01 is the usual last spring frost, about 277 days away. The first fall frost typically arrives around 09/11, about 100 frost-free days later.
Zone 5a (-20 to -15°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Big Timber, not a forecast for this year.
What to do before the first frost
Zone 5a around Big Timber has about 2 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.
Why 06/01 isn't a guarantee
06/01 is the middle of 30 years of NOAA records, not a promise. Plant by 05/15 and you're betting against frost in roughly 9 years out of 10. 06/21 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Big Timber compares
Big Timber's growing season runs about 100 days, ranking 39,718 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 311 of 392.
Learn more
zone vs. frost date explains why Zone 5a and Big Timber's frost date answer different questions, and the frost range explains how to read the range around Big Timber's dates instead of trusting one.