Mason, WI 54839 Frost Dates
54839, near Mason, WI: the frost window
Around 05/16 is the usual last spring frost, about 261 days away. Fall's first freeze usually shows up around 09/30, roughly 136 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Mason in Zone 4b (-25 to -20°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Mason's growing season runs out in roughly 5 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
05/16 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 05/27 and only about 1 year in 10 sees frost after that.
Mason against the rest of the dataset
At roughly 136 frost-free days, Mason places 37,810 of 40,283 ZIP codes in this dataset. Within WI, it ranks 769 of 860.
Learn more
Two guides worth reading on 54839: local microclimates, on what one yard in Mason can differ from the 54839 normal, and zone vs. frost date, on why Zone 4b and Mason's frost date answer different questions.