Sun Prairie, WI 53596 Frost Dates
Sun Prairie, WI: when does the frost end?
Typically, the last spring freeze lands around 05/01, roughly 246 days out. Fall's first freeze usually shows up around 10/10, roughly 160 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Sun Prairie in Zone 5a (-20 to -15°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
With roughly 6 weeks until Sun Prairie's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
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 04/16 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.
Sun Prairie against the rest of the dataset
Sun Prairie's growing season runs about 160 days, ranking 32,228 of 40,283 US ZIP codes measured here, longest to shortest. Within WI, it ranks 334 of 860.
Learn more
Before leaning on 53596's figures: local microclimates explains what one yard in Sun Prairie can differ from the 53596 normal, while zone vs. frost date explains why Zone 5a and Sun Prairie's frost date answer different questions.