Marathon, IA 50565 Frost Dates
Marathon, IA: when does the frost end?
Around 04/30 is the usual last spring frost, about 245 days away. Fall's first freeze usually shows up around 10/05, roughly 159 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Marathon in Zone 5a (-20 to -15°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 5 weeks until Marathon's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/30 isn't a guarantee
04/30 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/14 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/11 and only about 1 year in 10 sees frost after that.
Marathon against the rest of the dataset
About 159 days separate Marathon's last and first frost, putting it 32,781 of 40,283 ZIP codes nationally. Within IA, it ranks 801 of 1,042.
Learn more
Before leaning on 50565's figures: local microclimates explains what one yard in Marathon can differ from the 50565 normal, while zone vs. frost date explains why Zone 5a and Marathon's frost date answer different questions.