Mystic, IA 52574 Frost Dates
Frost dates for Mystic, IA, ZIP 52574
Around 04/18 is the usual last spring frost, about 233 days away. The first fall frost typically arrives around 10/23, about 187 frost-free days later.
Zone 5b (-15 to -10°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Mystic, not a forecast for this year.
What to do before the first frost
Zone 5b around Mystic has about 8 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 04/18 isn't a guarantee
04/18 is the middle of 30 years of NOAA records, not a promise. Plant by 04/04 and you're betting against frost in roughly 9 years out of 10. 05/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Mystic compares
At roughly 187 frost-free days, Mystic places 22,589 of 40,283 ZIP codes in this dataset. Within IA, it ranks 22 of 1,042.
Learn more
zone vs. frost date explains why Zone 5b and Mystic's frost date answer different questions, and the frost range explains how to read the range around Mystic's dates instead of trusting one.