Plymouth, IA 50464 Frost Dates
Plymouth, IA: when does the frost end?
Around 05/03 is the usual last spring frost, about 248 days away. Fall's first freeze usually shows up around 10/01, roughly 150 days after the last spring frost.
Plymouth sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
With roughly 5 weeks until Plymouth's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/03 isn't a guarantee
05/03 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/19 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/15 and only about 1 year in 10 sees frost after that.
Plymouth against the rest of the dataset
Plymouth's growing season runs about 150 days, ranking 35,392 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 1,012 of 1,042.
Learn more
Before leaning on 50464's figures: zone vs. frost date explains why Zone 5a and Plymouth's frost date answer different questions, while the frost range explains how to read the range around Plymouth's dates instead of trusting one.