Morrison, CO 80457 Frost Dates
Morrison, CO: when does the frost end?
Around 05/23 is the usual last spring frost, about 268 days away. Fall's first freeze usually shows up around 09/22, roughly 118 days after the last spring frost.
Zone 5b (-15 to -10°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 Morrison, not a forecast for this year.
Stretching the season past the first frost
With roughly 4 weeks until Morrison's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/23 isn't a guarantee
05/23 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/09 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/10 and only about 1 year in 10 sees frost after that.
Morrison against the rest of the dataset
About 118 days separate Morrison's last and first frost, putting it 39,231 of 40,283 ZIP codes nationally. Within CO, it ranks 474 of 624.
Learn more
Before leaning on 80457's figures: the frost range explains how to read the range around Morrison's dates instead of trusting one, while local microclimates explains what one yard in Morrison can differ from the 80457 normal.