Twin Bridges, MT 59754 Frost Dates
Frost dates for Twin Bridges, MT, ZIP 59754
Typically, the last spring freeze lands around 06/08, roughly 284 days out. The first fall frost typically arrives around 09/02, about 82 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 Twin Bridges, not a forecast for this year.
What to do before the first frost
Zone 5a around Twin Bridges has about 1 week 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
06/08 is the middle of 30 years of NOAA records, not a promise. Plant by 05/22 and you're betting against frost in roughly 9 years out of 10. 07/01 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Twin Bridges compares
Twin Bridges's growing season runs about 82 days, ranking 40,035 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 360 of 392.
Learn more
zone vs. frost date explains why Zone 5a and Twin Bridges's frost date answer different questions, and the frost range explains how to read the range around Twin Bridges's dates instead of trusting one.