It's growing season in Denver, CO

Denver's average last spring frost is around May 4, and its first fall frost around Oct 8 — a growing season of roughly 157 days. These figures come from the nearest NOAA station with long-term records (Denver-Stapleton, CO).

These are 1991–2020 averages, not guarantees: about half of years see a frost a little later in spring or earlier in fall. Cautious gardeners wait a week or two past the last-frost date before setting out frost-tender plants, or keep row cover handy for surprise cold snaps.

To build a planting calendar, count backward from the last spring frost for indoor seed-starting, and forward from the first fall frost for crops that need time to mature before cold returns.