Frost Dates for Denver, CO
In Denver, CO, the average last spring frost is around May 4 and the average first fall frost around Oct 8, for a growing season of about 156 days. For frost-tender plants, wait until May 16, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Denver-Stapleton, CO weather station, under 1 mile away, elevation 5,286 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 16 | Sep 25 |
| 20% | May 11 | Sep 30 |
| 30% | May 8 | Oct 3 |
| 40% | May 6 | Oct 6 |
| 50% | May 4 | Oct 8 |
| 60% | May 2 | Oct 11 |
| 70% | Apr 29 | Oct 14 |
| 80% | Apr 24 | Oct 17 |
| 90% | Apr 20 | Oct 20 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 12 | Oct 1 |
| Frost / freeze (32°F) | May 4 | Oct 8 |
| Hard freeze (28°F) | Apr 22 | Oct 18 |
Planting calendar for Denver
Transplant May 11 – May 25
Transplant May 18 – Jun 1
Transplant May 18 – Jun 1
Transplant May 11 – May 25
Sow or transplant May 11 – May 25
Sow or transplant May 11 – May 25
Sow or transplant May 18 – Jun 1
Sow or transplant Apr 6 – Apr 20
Fall sowing Aug 13 – Sep 10
Fall sowing Aug 13 – Sep 3
Fall sowing Jul 30 – Aug 13
Sow or transplant Apr 6 – Apr 20
Fall sowing Jul 30 – Aug 27
Transplant Apr 20 – May 4
Fall sowing Jul 16 – Jul 30
Transplant Apr 13 – Apr 27
Fall sowing Jul 16 – Jul 30
Fall sowing Jul 16 – Jul 30
Fall sowing Aug 27 – Sep 17
Fall sowing Jul 30 – Aug 13
Plant Apr 6 – Apr 20
Based on the average last frost (May 4) and first frost (Oct 8). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.