Castle Rock, CO 80104 Frost Dates
Castle Rock, CO: when does the frost end?
The last spring frost here typically falls around 05/09, about 254 days from today. Fall's first freeze usually shows up around 10/02, roughly 143 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 Castle Rock, not a forecast for this year.
Stretching the season past the first frost
With roughly 5 weeks until Castle Rock's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
05/09 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/24 and only about 1 year in 10 sees frost after that.
Castle Rock against the rest of the dataset
About 143 days separate Castle Rock's last and first frost, putting it 36,483 of 40,283 ZIP codes nationally. Within CO, it ranks 377 of 624.
Learn more
Before leaning on 80104's figures: the frost range explains how to read the range around Castle Rock's dates instead of trusting one, while local microclimates explains what one yard in Castle Rock can differ from the 80104 normal.