Frost dates for Pomona/fairplex, CA
At Pomona/fairplex, the median last spring frost (32°F) is Jan 8 and the median first fall frost is Dec 28, for a typical growing season of 354 days. For a 90% chance that the last frost has passed, wait until Feb 18. Nearby ZIP codes are in USDA hardiness zone 10a.
- Jan 8Last spring frost (median)50% chance of 32°F after this date
- Feb 18Safer planting date10% chance of 32°F after this date
- Dec 28First fall frost (median)50% chance of 32°F by this date
- 354 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 29 | Feb 8 | Mar 9 |
| 32°F | Dec 14 | Jan 8 | Feb 18 |
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 21 | Dec 10 | Dec 26 |
| 32°F | Dec 5 | Dec 28 | Feb 2 |
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 | 264 days | 303 days | 342 days |
| 32°F | 315 days | 354 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 | 99% |
| 32°F | 65% |
| 28°F | 7% |
| 24°F | 0% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 91767 | 10a | 30 to 35°F | 3 km |
| 91768 | 10a | 30 to 35°F | 3 km |
| 91766 | 10a | 30 to 35°F | 4 km |
| 91773 | 10a | 30 to 35°F | 5 km |
| 91763 | 10a | 30 to 35°F | 6 km |
| 91711 | 10a | 30 to 35°F | 7 km |
| 91750 | 10a | 30 to 35°F | 7 km |
| 91724 | 10a | 30 to 35°F | 8 km |
| 91740 | 10a | 30 to 35°F | 9 km |
| 91789 | 10a | 30 to 35°F | 11 km |
| 91741 | 10a | 30 to 35°F | 11 km |
| 91723 | 10a | 30 to 35°F | 11 km |
| 91765 | 10a | 30 to 35°F | 12 km |
| 91791 | 10a | 30 to 35°F | 12 km |
| 91722 | 10a | 30 to 35°F | 13 km |
| 91792 | 10a | 30 to 35°F | 14 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 USC00047050, at 34.0817, -117.7658, elevation 304 m (999 ft).
- Data quality: Representative (10+ years), 16 years of freeze data.
- Average days per year at or below 32°F: 3.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ontario Intl Airport (16 km)
- Chino Airport (17 km)
- Anaheim (25 km)
- Fullerton Muni Airport (31 km)
- San Gabriel Fire Dept (31 km)
- Mount Wilson Cbs (33 km)
- Wrightwood (33 km)
- Riverside Muni Airport (33 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.