Watertown, MN 55388 Frost Dates
55388, near Watertown, MN: the frost window
Typically, the last spring freeze lands around 04/30, roughly 245 days out. Fall's first freeze usually shows up around 10/08, roughly 159 days after the last spring frost.
Watertown 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
Watertown's growing season runs out in roughly 6 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 Watertown's last frost
04/30 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/18 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/14 and only about 1 year in 10 sees frost after that.
Watertown against the rest of the dataset
Watertown's growing season runs about 159 days, ranking 32,645 of 40,283 US ZIP codes measured here, longest to shortest. Within MN, it ranks 253 of 943.
Learn more
Two guides worth reading on 55388: the frost range, on how to read the range around Watertown's dates instead of trusting one, and local microclimates, on what one yard in Watertown can differ from the 55388 normal.