Ottawa, IL 60557 Frost Dates
Frost dates for Ottawa, IL, ZIP 60557
Around 04/27 is the usual last spring frost, about 242 days away. The first fall frost typically arrives around 10/17, about 171 frost-free days later.
Zone 5b (-15 to -10°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 Ottawa, not a forecast for this year.
What to do before the first frost
Zone 5b around Ottawa 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.
How much risk comes with planting early here
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. 05/13 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Ottawa compares
About 171 days separate Ottawa's last and first frost, putting it 28,605 of 40,283 ZIP codes nationally. Within IL, it ranks 1,367 of 1,548.
Learn more
the frost range explains how to read the range around Ottawa's dates instead of trusting one, and local microclimates explains what one yard in Ottawa can differ from the 60557 normal.