Frost dates for Ontario Intl Airport, CA
At Ontario Intl Airport, the median last spring frost (32°F) is Jan 4 and the median first fall frost is Dec 30, for a typical growing season of 365 days. For a 90% chance that the last frost has passed, wait until Feb 7. Nearby ZIP codes are in USDA hardiness zone 10a.
- Jan 4Last spring frost (median)50% chance of 32°F after this date
- Feb 7Safer planting date10% chance of 32°F after this date
- Dec 30First fall frost (median)50% chance of 32°F by this date
- 365 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Dec 24 | Jan 27 | Feb 28 |
| 32°F | Dec 14 | Jan 4 | Feb 7 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Nov 27 | Dec 17 | Jan 17 |
| 32°F | Dec 11 | Dec 30 | Feb 1 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 282 days | 327 days | 358 days |
| 32°F | 339 days | 365 days | 365 days |
| 28°F | 365 days | 365 days | 365 days |
| 24°F | 365 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 93% |
| 32°F | 41% |
| 28°F | 4% |
| 24°F | 0% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 91764 | 10a | 30 to 35°F | 2 km |
| 91761 | 10a | 30 to 35°F | 2 km |
| 91730 | 10a | 30 to 35°F | 5 km |
| 91762 | 10a | 30 to 35°F | 6 km |
| 91786 | 10a | 30 to 35°F | 8 km |
| 91701 | 10a | 30 to 35°F | 9 km |
| 91752 | 10a | 30 to 35°F | 9 km |
| 91784 | 10a | 30 to 35°F | 11 km |
| 91737 | 10a | 30 to 35°F | 11 km |
| 92335 | 10a | 30 to 35°F | 13 km |
| 91739 | 10a | 30 to 35°F | 14 km |
| 92336 | 10a | 30 to 35°F | 16 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USW00003102, at 34.0561, -117.6003, elevation 289 m (949 ft).
- Data quality: Representative (10+ years), 14 years of freeze data.
- Average days per year at or below 32°F: 2.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Chino Airport (10 km)
- Pomona/fairplex (16 km)
- Riverside Muni Airport (19 km)
- Riverside Fire Station 3 (23 km)
- Riverside Citrus Exp. (24 km)
- Anaheim (31 km)
- Wrightwood (34 km)
- Redlands (37 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.