Onawa, IA 51040 Frost Dates
Frost dates for Onawa, IA, ZIP 51040
Around 05/01 is the usual last spring frost, about 246 days away. The first fall frost typically arrives around 10/03, about 154 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 Onawa, not a forecast for this year.
What to do before the first frost
Zone 5a around Onawa has about 5 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.
The actual range around Onawa's last frost
05/01 is the middle of 30 years of NOAA records, not a promise. Plant by 04/19 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 Onawa compares
At roughly 154 frost-free days, Onawa places 34,327 of 40,283 ZIP codes in this dataset. Within IA, it ranks 896 of 1,042.
Learn more
local microclimates explains what one yard in Onawa can differ from the 51040 normal, and zone vs. frost date explains why Zone 5a and Onawa's frost date answer different questions.