Alton, IN 40161 Frost Dates
40161, near Alton, IN: the frost window
Typically, the last spring freeze lands around 04/19, roughly 234 days out. Fall's first freeze usually shows up around 10/24, roughly 186 days after the last spring frost.
Alton sits in USDA Zone 7a (0 to 5°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
Alton's growing season runs out in roughly 8 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
04/19 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/04 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/02 and only about 1 year in 10 sees frost after that.
Alton against the rest of the dataset
Alton's growing season runs about 186 days, ranking 22,990 of 40,283 US ZIP codes measured here, longest to shortest. Within IN, it ranks 353 of 927.
Learn more
Two guides worth reading on 40161: local microclimates, on what one yard in Alton can differ from the 40161 normal, and zone vs. frost date, on why Zone 7a and Alton's frost date answer different questions.