Colby, WI 54421 Frost Dates
54421, near Colby, WI: the frost window
Typically, the last spring freeze lands around 05/13, roughly 258 days out. Fall's first freeze usually shows up around 09/26, roughly 136 days after the last spring frost.
Colby 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.
Stretching the season past the first frost
Colby's growing season runs out in roughly 4 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 Colby's last frost
05/13 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/29 and only about 1 year in 10 sees frost after that.
Colby against the rest of the dataset
Colby's growing season runs about 136 days, ranking 37,702 of 40,283 US ZIP codes measured here, longest to shortest. Within WI, it ranks 754 of 860.
Learn more
Two guides worth reading on 54421: the frost range, on how to read the range around Colby's dates instead of trusting one, and local microclimates, on what one yard in Colby can differ from the 54421 normal.