Mason City, NE 68855 Frost Dates
68855, near Mason City, NE: the frost window
Typically, the last spring freeze lands around 05/03, roughly 248 days out. Fall's first freeze usually shows up around 10/05, roughly 153 days after the last spring frost.
Mason City sits in USDA Zone 5b (-15 to -10°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
Mason City's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Mason City's last frost
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 05/18 and only about 1 year in 10 sees frost after that.
Mason City against the rest of the dataset
At roughly 153 frost-free days, Mason City places 34,650 of 40,283 ZIP codes in this dataset. Within NE, it ranks 496 of 605.
Learn more
Two guides worth reading on 68855: zone vs. frost date, on why Zone 5b and Mason City's frost date answer different questions, and the frost range, on how to read the range around Mason City's dates instead of trusting one.