Sullivan, WI 53178 Frost Dates
Frost dates for Sullivan, WI, ZIP 53178
The last spring frost here typically falls around 05/03, about 248 days from today. The first fall frost typically arrives around 10/09, about 157 frost-free days later.
Sullivan sits in USDA Zone 5b (-15 to -10°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.
What to do before the first frost
Zone 5b around Sullivan has about 6 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 05/03 isn't a guarantee
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/18 and you're betting against frost in roughly 9 years out of 10. 05/21 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Sullivan compares
At roughly 157 frost-free days, Sullivan places 33,412 of 40,283 ZIP codes in this dataset. Within WI, it ranks 402 of 860.
Learn more
the frost range explains how to read the range around Sullivan's dates instead of trusting one, and local microclimates explains what one yard in Sullivan can differ from the 53178 normal.