Jamestown, CO 80455 Frost Dates
Frost dates for Jamestown, CO, ZIP 80455
Typically, the last spring freeze lands around 06/21, roughly 297 days out. The first fall frost typically arrives around 09/02, about 71 frost-free days later.
The USDA Plant Hardiness Zone Map puts Jamestown in Zone 5b (-15 to -10°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 5b around Jamestown has about 1 week left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 06/21 isn't a guarantee
06/21 is the middle of 30 years of NOAA records, not a promise. Plant by 06/07 and you're betting against frost in roughly 9 years out of 10. 07/04 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Jamestown compares
At roughly 71 frost-free days, Jamestown places 40,118 of 40,283 ZIP codes in this dataset. Within CO, it ranks 579 of 624.
Learn more
local microclimates explains what one yard in Jamestown can differ from the 80455 normal, and zone vs. frost date explains why Zone 5b and Jamestown's frost date answer different questions.