Alton, IN 40170 Frost Dates
Alton, IN: when does the frost end?
Around 04/02 is the usual last spring frost, about 217 days away. Fall's first freeze usually shows up around 11/07, roughly 218 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Alton in Zone 7a (0 to 5°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 10 weeks until Alton's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/02 isn't a guarantee
04/02 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/16 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/20 and only about 1 year in 10 sees frost after that.
Alton against the rest of the dataset
Alton's growing season runs about 218 days, ranking 13,360 of 40,283 US ZIP codes measured here, longest to shortest. Within IN, it ranks 26 of 927.
Learn more
Before leaning on 40170's figures: zone vs. frost date explains why Zone 7a and Alton's frost date answer different questions, while the frost range explains how to read the range around Alton's dates instead of trusting one.