Sidney, MT 59217 Frost Dates
Sidney, MT: when does the frost end?
Typically, the last spring freeze lands around 05/12, roughly 257 days out. Fall's first freeze usually shows up around 09/25, roughly 135 days after the last spring frost.
Sidney sits in USDA Zone 4a (-30 to -25°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
With roughly 4 weeks until Sidney's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/12 isn't a guarantee
05/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/01 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.
Sidney against the rest of the dataset
About 135 days separate Sidney's last and first frost, putting it 37,846 of 40,283 ZIP codes nationally. Within MT, it ranks 96 of 392.
Learn more
Before leaning on 59217's figures: the frost range explains how to read the range around Sidney's dates instead of trusting one, while local microclimates explains what one yard in Sidney can differ from the 59217 normal.