Frost dates for Henshaw Dam, CA
At Henshaw Dam, the median last spring frost (32°F) is Apr 18 and the median first fall frost is Oct 26, for a typical growing season of 189 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zones 8b to 9a.
- Apr 18Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 26First fall frost (median)50% chance of 32°F by this date
- 189 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 24 | May 17 | Jun 25 |
| 32°F | Mar 30 | Apr 18 | May 14 |
| 28°F | Feb 11 | Mar 14 | Apr 13 |
| 24°F | Jan 2 | Feb 5 | Mar 2 |
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 | Sep 18 | Oct 8 | Oct 25 |
| 32°F | Oct 9 | Oct 26 | Nov 13 |
| 28°F | Oct 25 | Nov 14 | Dec 2 |
| 24°F | Nov 11 | Dec 3 | Dec 26 |
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 | 101 days | 142 days | 171 days |
| 32°F | 155 days | 189 days | 216 days |
| 28°F | 203 days | 239 days | 276 days |
| 24°F | 261 days | 299 days | 338 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 99% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 92070 | 9a | 20 to 25°F | 6 km |
| 92086 | 8b | 15 to 20°F | 15 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 USC00043914, at 33.2372, -116.7614, elevation 823 m (2,700 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 105.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Palomar Mountain Obsy (17 km)
- Julian Cdf (24 km)
- Valley Center 1n (26 km)
- Ramona Airport (26 km)
- San Pasqual Animal Pk (27 km)
- Ramona Fire Dept (29 km)
- Cuyamaca (32 km)
- Escondido #2 (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.