Portage, WI 53901 Frost Dates
When can you plant in Portage, WI?
Typically, the last spring freeze lands around 04/28, roughly 243 days out. The first fall frost typically arrives around 10/10, about 164 frost-free days later.
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 Portage, not a forecast for this year.
What to do before the first frost
About 6 weeks of growing season left in Portage before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 04/28 isn't a guarantee
04/28 is the middle of 30 years of NOAA records, not a promise. Plant by 04/14 and you're betting against frost in roughly 9 years out of 10. 05/12 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Portage compares
About 164 days separate Portage's last and first frost, putting it 30,880 of 40,283 ZIP codes nationally. Within WI, it ranks 207 of 860.
Learn more
zone vs. frost date covers why Zone 5a and Portage's frost date answer different questions. the frost range covers how to read the range around Portage's dates instead of trusting one.