Alta, IA 51002 Frost Dates
Frost dates for Alta, IA, ZIP 51002
Around 05/04 is the usual last spring frost, about 249 days away. The first fall frost typically arrives around 10/04, about 152 frost-free days later.
Alta sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 5a around Alta 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.
Why 05/04 isn't a guarantee
05/04 is the middle of 30 years of NOAA records, not a promise. Plant by 04/20 and you're betting against frost in roughly 9 years out of 10. 05/17 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Alta compares
Alta's growing season runs about 152 days, ranking 34,783 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 949 of 1,042.
Learn more
local microclimates explains what one yard in Alta can differ from the 51002 normal, and zone vs. frost date explains why Zone 5a and Alta's frost date answer different questions.