Richey, MT 59243 Frost Dates
Frost dates for Richey, MT, ZIP 59243
Around 05/11 is the usual last spring frost, about 256 days away. The first fall frost typically arrives around 09/27, about 137 frost-free days later.
The USDA Plant Hardiness Zone Map puts Richey in Zone 4a (-30 to -25°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 4a around Richey 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.
Why 05/11 isn't a guarantee
05/11 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. 05/25 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Richey compares
Richey's growing season runs about 137 days, ranking 37,591 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 80 of 392.
Learn more
zone vs. frost date explains why Zone 4a and Richey's frost date answer different questions, and the frost range explains how to read the range around Richey's dates instead of trusting one.