Williams, IA 50271 Frost Dates
Williams, IA: when does the frost end?
Typically, the last spring freeze lands around 05/03, roughly 248 days out. Fall's first freeze usually shows up around 10/02, roughly 150 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Williams in Zone 5a (-20 to -15°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 5 weeks until Williams's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Williams's last frost
05/03 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/20 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/16 and only about 1 year in 10 sees frost after that.
Williams against the rest of the dataset
Williams's growing season runs about 150 days, ranking 35,405 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 1,015 of 1,042.
Learn more
Before leaning on 50271's figures: the frost range explains how to read the range around Williams's dates instead of trusting one, while local microclimates explains what one yard in Williams can differ from the 50271 normal.