Frost Dates for Windsor, CO
In Windsor, CO, the average last spring frost is around May 3 and the average first fall frost around Oct 6, for a growing season of about 154 days. For frost-tender plants, wait until May 15, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Ft Collins 4 E, CO weather station, 9 miles away, elevation 4,920 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 15 | Sep 22 |
| 20% | May 11 | Sep 27 |
| 30% | May 8 | Oct 1 |
| 40% | May 6 | Oct 3 |
| 50% | May 3 | Oct 6 |
| 60% | May 1 | Oct 9 |
| 70% | Apr 29 | Oct 11 |
| 80% | Apr 26 | Oct 14 |
| 90% | Apr 21 | Oct 17 |
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 14 | Sep 27 |
| Frost / freeze (32°F) | May 3 | Oct 6 |
| Hard freeze (28°F) | Apr 23 | Oct 14 |
Planting calendar for Windsor
Transplant May 10 – May 24
Transplant May 17 – May 31
Transplant May 17 – May 31
Transplant May 10 – May 24
Sow or transplant May 10 – May 24
Sow or transplant May 10 – May 24
Sow or transplant May 17 – May 31
Sow or transplant Apr 5 – Apr 19
Fall sowing Aug 11 – Sep 8
Fall sowing Aug 11 – Sep 1
Fall sowing Jul 28 – Aug 11
Sow or transplant Apr 5 – Apr 19
Fall sowing Jul 28 – Aug 25
Transplant Apr 19 – May 3
Fall sowing Jul 14 – Jul 28
Transplant Apr 12 – Apr 26
Fall sowing Jul 14 – Jul 28
Fall sowing Jul 14 – Jul 28
Fall sowing Aug 25 – Sep 15
Fall sowing Jul 28 – Aug 11
Plant Apr 5 – Apr 19
Based on the average last frost (May 3) and first frost (Oct 6). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.