Mount Vernon, IA 52314 Frost Dates
52314, near Mount Vernon, IA: the frost window
Typically, the last spring freeze lands around 04/28, roughly 243 days out. Fall's first freeze usually shows up around 10/12, roughly 166 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 Mount Vernon, not a forecast for this year.
Stretching the season past the first frost
Mount Vernon's growing season runs out in roughly 6 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/28 isn't a guarantee
04/28 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 05/13 and only about 1 year in 10 sees frost after that.
Mount Vernon against the rest of the dataset
At roughly 166 frost-free days, Mount Vernon places 30,366 of 40,283 ZIP codes in this dataset. Within IA, it ranks 455 of 1,042.
Learn more
Two guides worth reading on 52314: local microclimates, on what one yard in Mount Vernon can differ from the 52314 normal, and zone vs. frost date, on why Zone 5a and Mount Vernon's frost date answer different questions.