Grafton, IA 50440 Frost Dates
When can you plant in Grafton, IA?
The last spring frost here typically falls around 05/04, about 249 days from today. The first fall frost typically arrives around 10/04, about 152 frost-free days later.
Zone 5a (-20 to -15°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 Grafton, not a forecast for this year.
What to do before the first frost
About 5 weeks of growing season left in Grafton before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/04 isn't a guarantee
05/04 is the middle of 30 years of NOAA records, not a promise. Plant by 04/21 and you're betting against frost in roughly 9 years out of 10. 05/16 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Grafton compares
Grafton's growing season runs about 152 days, ranking 34,899 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 960 of 1,042.
Learn more
the frost range covers how to read the range around Grafton's dates instead of trusting one. local microclimates covers what one yard in Grafton can differ from the 50440 normal.