Glasgow, MT 59240 Frost Dates
59240, near Glasgow, MT: the frost window
Typically, the last spring freeze lands around 05/13, roughly 258 days out. Fall's first freeze usually shows up around 09/27, roughly 134 days after the last spring frost.
Glasgow sits in USDA Zone 3b (-35 to -30°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
Glasgow's growing season runs out in roughly 4 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Glasgow's last frost
05/13 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/02 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/26 and only about 1 year in 10 sees frost after that.
Glasgow against the rest of the dataset
At roughly 134 frost-free days, Glasgow places 37,963 of 40,283 ZIP codes in this dataset. Within MT, it ranks 110 of 392.
Learn more
Two guides worth reading on 59240: the frost range, on how to read the range around Glasgow's dates instead of trusting one, and local microclimates, on what one yard in Glasgow can differ from the 59240 normal.