Johnstown, CO 80534 Frost Dates
Frost dates for Johnstown, CO, ZIP 80534
Around 05/10 is the usual last spring frost, about 255 days away. The first fall frost typically arrives around 10/01, about 142 frost-free days later.
Johnstown sits in USDA Zone 5b (-15 to -10°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 5b around Johnstown has about 5 weeks 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 05/10 isn't a guarantee
05/10 is the middle of 30 years of NOAA records, not a promise. Plant by 04/30 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 Johnstown compares
At roughly 142 frost-free days, Johnstown places 36,710 of 40,283 ZIP codes in this dataset. Within CO, it ranks 388 of 624.
Learn more
local microclimates explains what one yard in Johnstown can differ from the 80534 normal, and zone vs. frost date explains why Zone 5b and Johnstown's frost date answer different questions.