Frost dates for Hetch Hetchy, CA
At Hetch Hetchy, the median last spring frost (32°F) is Apr 16 and the median first fall frost is Nov 12, for a typical growing season of 208 days. For a 90% chance that the last frost has passed, wait until May 12. Nearby ZIP codes are in USDA hardiness zones 6a to 6b.
- Apr 16Last spring frost (median)50% chance of 32°F after this date
- May 12Safer planting date10% chance of 32°F after this date
- Nov 12First fall frost (median)50% chance of 32°F by this date
- 208 daysGrowing season (median)between 32°F freezes
USDA hardiness zone 6a (-10 to -5°F) · see all zone 6a frost dates
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 17 | May 5 | May 31 |
| 32°F | Mar 24 | Apr 16 | May 12 |
| 28°F | Feb 19 | Mar 25 | Apr 17 |
| 24°F | Jan 6 | Feb 22 | Mar 28 |
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 11 | Oct 29 | Nov 12 |
| 32°F | Oct 24 | Nov 12 | Dec 1 |
| 28°F | Nov 9 | Nov 28 | Dec 18 |
| 24°F | Nov 25 | Dec 19 | Jan 27 |
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 | 143 days | 172 days | 199 days |
| 32°F | 175 days | 208 days | 235 days |
| 28°F | 216 days | 249 days | 285 days |
| 24°F | 257 days | 297 days | 349 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 |
|---|---|---|---|
| 95321 | 6a | -10 to -5°F | 6 km |
| 95364 | 6b | -5 to 0°F | 29 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 USC00043939, at 37.9614, -119.7831, elevation 1180 m (3,870 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 70.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Cherry Valley Dam (12 km)
- Yosemite Village 12 W (23 km)
- Yosemite Park HQ (29 km)
- Tuolumne Meadows Ranger Station (40 km)
- Groveland 2 (41 km)
- So Entrance Yosemite National Park (52 km)
- Sonora (53 km)
- Calaveras Big Trees (58 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.