Frost dates for 91743Guasti, CA
Frost occurs in about 41% of years near Guasti, based on NOAA 1991-2020 records for the Ontario Intl Ap, CA station.
Frost occurs in about 41% of years. Frost-tender plants can usually grow year-round, but cover them if a rare cold snap is forecast.
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Dec 24 · Jan 27 · Feb 28 | Nov 27 · Dec 17 · Jan 17 | 327 days | 93% |
| Frost / freeze (32°F) | Dec 14 · Jan 4 · Feb 7 | Dec 11 · Dec 30 · Feb 1 | 365 days | 41% |
| Hard freeze (28°F) | — | — | 365 days | 4% |
Where these dates come from
ZIP code 91743 is matched to the NOAA station Ontario Intl Ap, CA, 1.6 km away, at 949 ft elevation (22 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Ontario Intl Ap, CA (used) | 949 ft | Jan 4 | Dec 30 |
| Chino Ap, CA | 650 ft | Jan 17 | Dec 19 |
| Pomona/Fairplex, CA | 999 ft | Jan 8 | Dec 28 |
| Riverside Muni Ap, CA | 805 ft | Jan 9 | Dec 30 |
Frost dates near Guasti
- Ontario, CA 91764 · last Jan 8, first Dec 28
- Rancho Cucamonga, CA 91729 · last Jan 8, first Dec 28
- Upland, CA 91785 · last Jan 8, first Dec 28
- Mira Loma, CA 91752 · last Jan 9, first Dec 30
- Montclair, CA 91763 · last Jan 8, first Dec 28
- Chino, CA 91710 · last Jan 17, first Dec 19
- Fontana, CA 92337 · last Jan 10, first Jan 2
- Claremont, CA 91711 · last Jan 8, first Dec 28
Frequently asked questions
- When is the last frost in Guasti, CA?
- Frost occurs in about 41% of years at the nearest NOAA station (Ontario Intl Ap, CA), so there is no reliable average last frost date.
- When is the first frost in Guasti, CA?
- Frost occurs in about 41% of years at the nearest NOAA station.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.