East Helena, MT 59634 Frost Dates
59634, near East Helena, MT: the frost window
Typically, the last spring freeze lands around 06/18, roughly 294 days out. Fall's first freeze usually shows up around 09/05, roughly 81 days after the last spring frost.
East Helena sits in USDA Zone 4b (-25 to -20°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
East Helena'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.
How much risk comes with planting early here
06/18 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 07/03 and only about 1 year in 10 sees frost after that.
East Helena against the rest of the dataset
At roughly 81 frost-free days, East Helena places 40,039 of 40,283 ZIP codes in this dataset. Within MT, it ranks 361 of 392.
Learn more
Two guides worth reading on 59634: the frost range, on how to read the range around East Helena's dates instead of trusting one, and local microclimates, on what one yard in East Helena can differ from the 59634 normal.