Colorado frost dates

Across Colorado, the average last spring frost is around May 5 and the average first fall frost around October 1 — roughly 149 frost-free days. USDA zones 3b, 4b, 5a, 5b, 6a, 7a.

Risk you accept	Last spring frost by	First fall frost by
Cautious (~10%)	May 19	September 17
Average (~50%)	May 5	October 1
Gambler (~90%)	April 21	October 15

Colorado spans a wide range of elevations and climates — your town’s dates can differ from the state average by two weeks or more. Look up your exact ZIP.

→ Turn these into sowing dates with the Colorado planting calendar, or look up an exact ZIP code.

Statewide average from NOAA/NCEI freeze normals. Cautious/gambler dates are about two weeks either side of the average.