Frost Dates for Rancho Cucamonga, CA
In Rancho Cucamonga, CA, the average last spring frost is around Jan 4 and the average first fall frost around Dec 30, for a growing season of about 365 days. For frost-tender plants, wait until Feb 7, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Ontario Intl. Airport, CA weather station, 5 miles away, elevation 949 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% | Feb 7 | Dec 11 |
| 20% | Jan 25 | Dec 18 |
| 30% | Jan 13 | Dec 22 |
| 40% | Jan 8 | Dec 25 |
| 50% | Jan 4 | Dec 30 |
| 60% | Dec 31 | Jan 3 |
| 70% | Dec 27 | Jan 7 |
| 80% | Dec 21 | Jan 15 |
| 90% | Dec 14 | Feb 1 |
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) | Jan 27 | Dec 17 |
| Frost / freeze (32°F) | Jan 4 | Dec 30 |
| Hard freeze (28°F) | — | — |
Planting calendar for Rancho Cucamonga
Transplant Jan 11 – Jan 25
Transplant Jan 18 – Feb 1
Transplant Jan 18 – Feb 1
Transplant Jan 11 – Jan 25
Sow or transplant Jan 11 – Jan 25
Sow or transplant Jan 11 – Jan 25
Sow or transplant Jan 18 – Feb 1
Sow or transplant Dec 7 – Dec 21
Fall sowing Nov 4 – Dec 2
Fall sowing Nov 4 – Nov 25
Fall sowing Oct 21 – Nov 4
Sow or transplant Dec 7 – Dec 21
Fall sowing Oct 21 – Nov 18
Transplant Dec 21 – Jan 4
Fall sowing Oct 7 – Oct 21
Transplant Dec 14 – Dec 28
Fall sowing Oct 7 – Oct 21
Fall sowing Oct 7 – Oct 21
Fall sowing Nov 18 – Dec 9
Fall sowing Oct 21 – Nov 4
Plant Dec 7 – Dec 21
Based on the average last frost (Jan 4) and first frost (Dec 30). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.