Janesville, WI 53546 Frost Dates
Frost dates for Janesville, WI, ZIP 53546
Around 05/01 is the usual last spring frost, about 246 days away. The first fall frost typically arrives around 10/12, about 162 frost-free days later.
Zone 5b (-15 to -10°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 Janesville, not a forecast for this year.
What to do before the first frost
Zone 5b around Janesville 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 05/01 isn't a guarantee
05/01 is the middle of 30 years of NOAA records, not a promise. Plant by 04/17 and you're betting against frost in roughly 9 years out of 10. 05/16 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Janesville compares
At roughly 162 frost-free days, Janesville places 31,600 of 40,283 ZIP codes in this dataset. Within WI, it ranks 251 of 860.
Learn more
local microclimates explains what one yard in Janesville can differ from the 53546 normal, and zone vs. frost date explains why Zone 5b and Janesville's frost date answer different questions.