Arthur, IA 51431 Frost Dates
Frost dates for Arthur, IA, ZIP 51431
Typically, the last spring freeze lands around 04/27, roughly 242 days out. The first fall frost typically arrives around 10/12, about 167 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 Arthur, not a forecast for this year.
What to do before the first frost
Zone 5a around Arthur 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.
The actual range around Arthur's last frost
04/27 is the middle of 30 years of NOAA records, not a promise. Plant by 04/12 and you're betting against frost in roughly 9 years out of 10. 05/11 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Arthur compares
Arthur's growing season runs about 167 days, ranking 30,204 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 432 of 1,042.
Learn more
local microclimates explains what one yard in Arthur can differ from the 51431 normal, and zone vs. frost date explains why Zone 5a and Arthur's frost date answer different questions.