Marion, IA 52407 Frost Dates
Frost dates for Marion, IA, ZIP 52407
Around 04/28 is the usual last spring frost, about 243 days away. The first fall frost typically arrives around 10/12, about 166 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 Marion, not a forecast for this year.
What to do before the first frost
Zone 5b around Marion has about 6 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 04/28 isn't a guarantee
04/28 is the middle of 30 years of NOAA records, not a promise. Plant by 04/14 and you're betting against frost in roughly 9 years out of 10. 05/13 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Marion compares
Marion's growing season runs about 166 days, ranking 30,286 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 442 of 1,042.
Learn more
local microclimates explains what one yard in Marion can differ from the 52407 normal, and zone vs. frost date explains why Zone 5b and Marion's frost date answer different questions.