Watertown, SD 57201 Frost Dates
Watertown, SD: when does the frost end?
Around 05/07 is the usual last spring frost, about 252 days away. Fall's first freeze usually shows up around 09/30, roughly 145 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
With roughly 5 weeks until Watertown's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Watertown's last frost
05/07 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/26 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/20 and only about 1 year in 10 sees frost after that.
Watertown against the rest of the dataset
Watertown's growing season runs about 145 days, ranking 36,164 of 40,283 US ZIP codes measured here, longest to shortest. Within SD, it ranks 230 of 378.
Learn more
Before leaning on 57201's figures: zone vs. frost date explains why Zone 4b and Watertown's frost date answer different questions, while the frost range explains how to read the range around Watertown's dates instead of trusting one.