Morrison, CO 80402 Frost Dates
80402, near Morrison, CO: the frost window
Typically, the last spring freeze lands around 05/08, roughly 253 days out. Fall's first freeze usually shows up around 10/03, roughly 147 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Morrison in Zone 6a (-10 to -5°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
Morrison'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.
How much risk comes with planting early here
05/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/22 and only about 1 year in 10 sees frost after that.
Morrison against the rest of the dataset
About 147 days separate Morrison's last and first frost, putting it 35,968 of 40,283 ZIP codes nationally. Within CO, it ranks 355 of 624.
Learn more
Two guides worth reading on 80402: zone vs. frost date, on why Zone 6a and Morrison's frost date answer different questions, and the frost range, on how to read the range around Morrison's dates instead of trusting one.