Hillsboro, WI 54634 Frost Dates
When can you plant in Hillsboro, WI?
Around 05/12 is the usual last spring frost, about 257 days away. The first fall frost typically arrives around 09/29, about 138 frost-free days later.
Hillsboro sits in USDA Zone 4b (-25 to -20°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
About 5 weeks of growing season left in Hillsboro before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/12 isn't a guarantee
05/12 is the middle of 30 years of NOAA records, not a promise. Plant by 04/28 and you're betting against frost in roughly 9 years out of 10. 05/26 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Hillsboro compares
Hillsboro's growing season runs about 138 days, ranking 37,407 of 40,283 US ZIP codes measured here, longest to shortest. Within WI, it ranks 744 of 860.
Learn more
local microclimates covers what one yard in Hillsboro can differ from the 54634 normal. zone vs. frost date covers why Zone 4b and Hillsboro's frost date answer different questions.