Northboro, IA 51647 Frost Dates
Frost dates for Northboro, IA, ZIP 51647
Around 04/19 is the usual last spring frost, about 234 days away. The first fall frost typically arrives around 10/15, about 177 frost-free days later.
The USDA Plant Hardiness Zone Map puts Northboro in Zone 5b (-15 to -10°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 5b around Northboro has about 7 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 04/19 isn't a guarantee
04/19 is the middle of 30 years of NOAA records, not a promise. Plant by 04/06 and you're betting against frost in roughly 9 years out of 10. 05/04 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Northboro compares
At roughly 177 frost-free days, Northboro places 26,312 of 40,283 ZIP codes in this dataset. Within IA, it ranks 127 of 1,042.
Learn more
zone vs. frost date explains why Zone 5b and Northboro's frost date answer different questions, and the frost range explains how to read the range around Northboro's dates instead of trusting one.