Hartford, WI 53027 Frost Dates
53027, near Hartford, WI: the frost window
Typically, the last spring freeze lands around 05/08, roughly 253 days out. Fall's first freeze usually shows up around 10/03, roughly 148 days after the last spring frost.
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 Hartford, not a forecast for this year.
Stretching the season past the first frost
Hartford's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Hartford's last frost
05/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/24 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/24 and only about 1 year in 10 sees frost after that.
Hartford against the rest of the dataset
About 148 days separate Hartford's last and first frost, putting it 35,689 of 40,283 ZIP codes nationally. Within WI, it ranks 602 of 860.
Learn more
Two guides worth reading on 53027: local microclimates, on what one yard in Hartford can differ from the 53027 normal, and zone vs. frost date, on why Zone 5a and Hartford's frost date answer different questions.