Alton, MO 65690 Frost Dates
When can you plant in Alton, MO?
Typically, the last spring freeze lands around 04/17, roughly 232 days out. The first fall frost typically arrives around 10/21, about 187 frost-free days later.
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.
What to do before the first frost
About 8 weeks of growing season left in Alton before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 04/17 isn't a guarantee
04/17 is the middle of 30 years of NOAA records, not a promise. Plant by 03/30 and you're betting against frost in roughly 9 years out of 10. 05/01 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Alton compares
About 187 days separate Alton's last and first frost, putting it 22,520 of 40,283 ZIP codes nationally. Within MO, it ranks 845 of 1,129.
Learn more
local microclimates covers what one yard in Alton can differ from the 65690 normal. zone vs. frost date covers why Zone 7a and Alton's frost date answer different questions.