Frost dates for Mount Wilson Cbs, CA
At Mount Wilson Cbs, the median last spring frost (32°F) is Apr 28 and the median first fall frost is Nov 15, for a typical growing season of 199 days. For a 90% chance that the last frost has passed, wait until May 27. Nearby ZIP codes are in USDA hardiness zone 10a.
- Apr 28Last spring frost (median)50% chance of 32°F after this date
- May 27Safer planting date10% chance of 32°F after this date
- Nov 15First fall frost (median)50% chance of 32°F by this date
- 199 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 | Apr 21 | May 15 | Jun 4 |
| 32°F | Mar 31 | Apr 28 | May 27 |
| 28°F | Feb 28 | Apr 8 | May 10 |
| 24°F | Jan 10 | Mar 12 | Apr 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 | Oct 3 | Oct 30 | Nov 19 |
| 32°F | Oct 18 | Nov 15 | Dec 9 |
| 28°F | Nov 5 | Dec 4 | Dec 29 |
| 24°F | Nov 26 | Dec 22 | Feb 20 |
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 | 134 days | 167 days | 200 days |
| 32°F | 164 days | 199 days | 238 days |
| 28°F | 196 days | 240 days | 287 days |
| 24°F | 241 days | 285 days | 351 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 96% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 91024 | 10a | 30 to 35°F | 7 km |
| 91016 | 10a | 30 to 35°F | 11 km |
| 91008 | 10a | 30 to 35°F | 13 km |
| 91010 | 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 USC00046006, at 34.2308, -118.0711, elevation 1740 m (5,710 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 50.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Pasadena (11 km)
- San Gabriel Fire Dept (17 km)
- Los Angeles Dwtn Usc Campus (25 km)
- Burbank Valley Pump Plant (26 km)
- Burbank Glendale Pasadena Airport (27 km)
- Pomona/fairplex (33 km)
- Pearblossom (34 km)
- Van Nuys Airport (39 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.