Big Timber, MT 59033 Frost Dates
59033, near Big Timber, MT: the frost window
Around 05/14 is the usual last spring frost, about 259 days away. Fall's first freeze usually shows up around 09/26, roughly 133 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 Big Timber, not a forecast for this year.
Stretching the season past the first frost
Big Timber'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.
How much risk comes with planting early here
05/14 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 05/27 and only about 1 year in 10 sees frost after that.
Big Timber against the rest of the dataset
Big Timber's growing season runs about 133 days, ranking 38,072 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 120 of 392.
Learn more
Two guides worth reading on 59033: zone vs. frost date, on why Zone 5a and Big Timber's frost date answer different questions, and the frost range, on how to read the range around Big Timber's dates instead of trusting one.