Frost Dates for Rialto, CA
In Rialto, CA, the average last spring frost is around Jan 10 and the average first fall frost around Jan 2, for a growing season of about 365 days. For frost-tender plants, wait until Feb 17, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Riverside Citrus Exp, CA weather station, 11 miles away, elevation 986 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 17 | Dec 11 |
| 20% | Feb 3 | Dec 20 |
| 30% | Jan 25 | Dec 26 |
| 40% | Jan 16 | Dec 30 |
| 50% | Jan 10 | Jan 2 |
| 60% | Jan 5 | Jan 7 |
| 70% | Jan 2 | Jan 15 |
| 80% | Dec 29 | Jan 24 |
| 90% | Dec 20 | Feb 7 |
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) | Feb 11 | Dec 13 |
| Frost / freeze (32°F) | Jan 10 | Jan 2 |
| Hard freeze (28°F) | — | — |
Planting calendar for Rialto
Transplant Jan 17 – Jan 31
Transplant Jan 24 – Feb 7
Transplant Jan 24 – Feb 7
Transplant Jan 17 – Jan 31
Sow or transplant Jan 17 – Jan 31
Sow or transplant Jan 17 – Jan 31
Sow or transplant Jan 24 – Feb 7
Sow or transplant Dec 13 – Dec 27
Fall sowing Nov 7 – Dec 5
Fall sowing Nov 7 – Nov 28
Fall sowing Oct 24 – Nov 7
Sow or transplant Dec 13 – Dec 27
Fall sowing Oct 24 – Nov 21
Transplant Dec 27 – Jan 10
Fall sowing Oct 10 – Oct 24
Transplant Dec 20 – Jan 3
Fall sowing Oct 10 – Oct 24
Fall sowing Oct 10 – Oct 24
Fall sowing Nov 21 – Dec 12
Fall sowing Oct 24 – Nov 7
Plant Dec 13 – Dec 27
Based on the average last frost (Jan 10) and first frost (Jan 2). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.