Frost Dates for Littleton, CO
In Littleton, CO, the average last spring frost is around May 2 and the average first fall frost around Oct 11, for a growing season of about 160 days. For frost-tender plants, wait until May 17, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Marston Fltr Plt, CO weather station, 3 miles away, elevation 5,610 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 17 | Sep 27 |
| 20% | May 12 | Oct 1 |
| 30% | May 8 | Oct 5 |
| 40% | May 5 | Oct 7 |
| 50% | May 2 | Oct 11 |
| 60% | Apr 30 | Oct 14 |
| 70% | Apr 28 | Oct 17 |
| 80% | Apr 25 | Oct 19 |
| 90% | Apr 20 | Oct 23 |
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 2 |
| Frost / freeze (32°F) | May 2 | Oct 11 |
| Hard freeze (28°F) | Apr 23 | Oct 21 |
Planting calendar for Littleton
Transplant May 9 – May 23
Transplant May 16 – May 30
Transplant May 16 – May 30
Transplant May 9 – May 23
Sow or transplant May 9 – May 23
Sow or transplant May 9 – May 23
Sow or transplant May 16 – May 30
Sow or transplant Apr 4 – Apr 18
Fall sowing Aug 16 – Sep 13
Fall sowing Aug 16 – Sep 6
Fall sowing Aug 2 – Aug 16
Sow or transplant Apr 4 – Apr 18
Fall sowing Aug 2 – Aug 30
Transplant Apr 18 – May 2
Fall sowing Jul 19 – Aug 2
Transplant Apr 11 – Apr 25
Fall sowing Jul 19 – Aug 2
Fall sowing Jul 19 – Aug 2
Fall sowing Aug 30 – Sep 20
Fall sowing Aug 2 – Aug 16
Plant Apr 4 – Apr 18
Based on the average last frost (May 2) and first frost (Oct 11). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.