Frost dates for Mount Diablo Junction, CA
At Mount Diablo Junction, the median last spring frost (32°F) is Mar 8 and the median first fall frost is Dec 22, for a typical growing season of 282 days. For a 90% chance that the last frost has passed, wait until Apr 15. Nearby ZIP codes are in USDA hardiness zone 9b.
- Mar 8Last spring frost (median)50% chance of 32°F after this date
- Apr 15Safer planting date10% chance of 32°F after this date
- Dec 22First fall frost (median)50% chance of 32°F by this date
- 282 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 | Mar 16 | Apr 19 | May 20 |
| 32°F | Jan 12 | Mar 8 | Apr 15 |
| 28°F | Dec 21 | Feb 8 | Mar 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 6 | Nov 29 | Dec 20 |
| 32°F | Nov 23 | Dec 22 | Feb 11 |
| 28°F | Dec 8 | Jan 16 | Mar 3 |
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 | 183 days | 221 days | 264 days |
| 32°F | 238 days | 282 days | 343 days |
| 28°F | 286 days | 364 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 | 96% |
| 28°F | 50% |
| 24°F | 7% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 94517 | 9b | 25 to 30°F | 4 km |
| 94528 | 9b | 25 to 30°F | 5 km |
| 94507 | 9b | 25 to 30°F | 7 km |
| 94506 | 9b | 25 to 30°F | 8 km |
| 94598 | 9b | 25 to 30°F | 9 km |
| 94526 | 9b | 25 to 30°F | 9 km |
| 94596 | 9b | 25 to 30°F | 9 km |
| 94588 | 9b | 25 to 30°F | 11 km |
| 94595 | 9b | 25 to 30°F | 12 km |
| 94583 | 9b | 25 to 30°F | 13 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 USC00045915, at 37.8792, -121.9303, elevation 661 m (2,170 ft).
- Data quality: Representative (10+ years), 25 years of freeze data.
- Average days per year at or below 32°F: 19.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Concord Buchanan Field (17 km)
- Concord Wastewater Plant (17 km)
- Antioch Pumping Plant #3 (19 km)
- Martinez Water Plant (22 km)
- Livermore (23 km)
- Livermore Muni Airport (23 km)
- Berkeley (29 km)
- Hayward Air Terminal (30 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.