Hysham, MT 59038 Frost Dates
When can you plant in Hysham, MT?
Around 05/10 is the usual last spring frost, about 255 days away. The first fall frost typically arrives around 09/29, about 141 frost-free days later.
The USDA Plant Hardiness Zone Map puts Hysham in Zone 4b (-25 to -20°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
About 5 weeks of growing season left in Hysham before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Hysham's last frost
05/10 is the middle of 30 years of NOAA records, not a promise. Plant by 04/28 and you're betting against frost in roughly 9 years out of 10. 05/22 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Hysham compares
Hysham's growing season runs about 141 days, ranking 36,988 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 63 of 392.
Learn more
the frost range covers how to read the range around Hysham's dates instead of trusting one. local microclimates covers what one yard in Hysham can differ from the 59038 normal.