Charter Oak, IA 51439 Frost Dates
Charter Oak, IA: when does the frost end?
Typically, the last spring freeze lands around 05/03, roughly 248 days out. Fall's first freeze usually shows up around 10/01, roughly 151 days after the last spring frost.
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 Charter Oak, not a forecast for this year.
Stretching the season past the first frost
With roughly 5 weeks until Charter Oak's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
05/03 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/21 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/16 and only about 1 year in 10 sees frost after that.
Charter Oak against the rest of the dataset
At roughly 151 frost-free days, Charter Oak places 35,130 of 40,283 ZIP codes in this dataset. Within IA, it ranks 977 of 1,042.
Learn more
Before leaning on 51439's figures: the frost range explains how to read the range around Charter Oak's dates instead of trusting one, while local microclimates explains what one yard in Charter Oak can differ from the 51439 normal.