Berlin, WI 54923 Frost Dates
54923, near Berlin, WI: the frost window
Around 05/01 is the usual last spring frost, about 246 days away. Fall's first freeze usually shows up around 10/08, roughly 158 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 Berlin, not a forecast for this year.
Stretching the season past the first frost
Berlin's growing season runs out in roughly 6 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/01 isn't a guarantee
05/01 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/19 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/16 and only about 1 year in 10 sees frost after that.
Berlin against the rest of the dataset
Berlin's growing season runs about 158 days, ranking 32,965 of 40,283 US ZIP codes measured here, longest to shortest. Within WI, it ranks 359 of 860.
Learn more
Two guides worth reading on 54923: zone vs. frost date, on why Zone 5a and Berlin's frost date answer different questions, and the frost range, on how to read the range around Berlin's dates instead of trusting one.