Morrison, CO 80001 Frost Dates
When can you plant in Morrison, CO?
Around 05/08 is the usual last spring frost, about 253 days away. The first fall frost typically arrives around 10/03, about 147 frost-free days later.
Zone 6a (-10 to -5°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.
What to do before the first frost
About 5 weeks of growing season left in Morrison before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
05/08 is the middle of 30 years of NOAA records, not a promise. Plant by 04/27 and you're betting against frost in roughly 9 years out of 10. 05/22 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Morrison compares
Morrison's growing season runs about 147 days, ranking 35,964 of 40,283 US ZIP codes measured here, longest to shortest. Within CO, it ranks 351 of 624.
Learn more
zone vs. frost date covers why Zone 6a and Morrison's frost date answer different questions. the frost range covers how to read the range around Morrison's dates instead of trusting one.