Jamestown, CO 80306 Frost Dates
80306, near Jamestown, CO: the frost window
Typically, the last spring freeze lands around 06/21, roughly 297 days out. Fall's first freeze usually shows up around 09/02, roughly 71 days after the last spring frost.
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 Jamestown, not a forecast for this year.
Stretching the season past the first frost
Jamestown's growing season runs out in roughly 1 week — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Jamestown's last frost
06/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 06/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 07/04 and only about 1 year in 10 sees frost after that.
Jamestown against the rest of the dataset
About 71 days separate Jamestown's last and first frost, putting it 40,117 of 40,283 ZIP codes nationally. Within CO, it ranks 578 of 624.
Learn more
Two guides worth reading on 80306: the frost range, on how to read the range around Jamestown's dates instead of trusting one, and local microclimates, on what one yard in Jamestown can differ from the 80306 normal.