Glasgow, MT 59230 Frost Dates
When can you plant in Glasgow, MT?
The last spring frost here typically falls around 05/03, about 248 days from today. The first fall frost typically arrives around 10/01, about 151 frost-free days later.
The USDA Plant Hardiness Zone Map puts Glasgow 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
About 5 weeks of growing season left in Glasgow before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/03 isn't a guarantee
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/19 and you're betting against frost in roughly 9 years out of 10. 05/15 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Glasgow compares
At roughly 151 frost-free days, Glasgow places 35,026 of 40,283 ZIP codes in this dataset. Within MT, it ranks 15 of 392.
Learn more
local microclimates covers what one yard in Glasgow can differ from the 59230 normal. zone vs. frost date covers why Zone 4a and Glasgow's frost date answer different questions.