Sheridan, MT 59749 Frost Dates
59749, near Sheridan, MT: the frost window
Around 06/08 is the usual last spring frost, about 284 days away. Fall's first freeze usually shows up around 09/02, roughly 82 days after the last spring frost.
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 Sheridan, not a forecast for this year.
Stretching the season past the first frost
Sheridan's growing season runs out in roughly 1 week — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 06/08 isn't a guarantee
06/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/22 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 07/01 and only about 1 year in 10 sees frost after that.
Sheridan against the rest of the dataset
At roughly 82 frost-free days, Sheridan places 40,033 of 40,283 ZIP codes in this dataset. Within MT, it ranks 358 of 392.
Learn more
Two guides worth reading on 59749: local microclimates, on what one yard in Sheridan can differ from the 59749 normal, and zone vs. frost date, on why Zone 5a and Sheridan's frost date answer different questions.