Frost dates for Alpine, CA
At Alpine, the median last spring frost (32°F) is Feb 12 and the median first fall frost is Dec 24, for a typical growing season of 317 days. For a 90% chance that the last frost has passed, wait until Mar 20. Nearby ZIP codes are in USDA hardiness zones 9b to 10a.
- Feb 12Last spring frost (median)50% chance of 32°F after this date
- Mar 20Safer planting date10% chance of 32°F after this date
- Dec 24First fall frost (median)50% chance of 32°F by this date
- 317 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 | Feb 15 | Mar 17 | Apr 16 |
| 32°F | Dec 29 | Feb 12 | Mar 20 |
| 28°F | Dec 12 | Jan 22 | Feb 23 |
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 15 | Dec 7 | Dec 23 |
| 32°F | Dec 2 | Dec 24 | Feb 3 |
| 28°F | Dec 10 | Jan 4 | 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 | 229 days | 263 days | 301 days |
| 32°F | 272 days | 317 days | 364 days |
| 28°F | 317 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 | 100% |
| 32°F | 90% |
| 28°F | 38% |
| 24°F | 6% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 91901 | 9b | 25 to 30°F | 5 km |
| 91935 | 10a | 30 to 35°F | 16 km |
| 91917 | 10a | 30 to 35°F | 22 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 USC00040136, at 32.8358, -116.7775, elevation 517 m (1,695 ft).
- Data quality: Representative (10+ years), 21 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
- El Capitan Dam (7 km)
- El Cajon (15 km)
- Ramona Fire Dept (23 km)
- Cuyamaca (25 km)
- Ramona Airport (26 km)
- Julian Cdf (32 km)
- San Diego Miramar NAS (33 km)
- Mount Laguna #3 (34 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.