Frost dates for Concord Wastewater Plant, CA
At Concord Wastewater Plant, the median last spring frost (32°F) is Jan 7 and the median first fall frost is Dec 19, for a typical growing season of 346 days. For a 90% chance that the last frost has passed, wait until Feb 1. Nearby ZIP codes are in USDA hardiness zone 9b.
- Jan 7Last spring frost (median)50% chance of 32°F after this date
- Feb 1Safer planting date10% chance of 32°F after this date
- Dec 19First fall frost (median)50% chance of 32°F by this date
- 346 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 | Jan 6 | Feb 9 | Mar 6 |
| 32°F | Dec 19 | Jan 7 | Feb 1 |
| 28°F | Dec 14 | Dec 31 | Jan 20 |
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 2 | Dec 24 |
| 32°F | Dec 1 | Dec 19 | Jan 12 |
| 28°F | Dec 10 | Dec 29 | Jan 14 |
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 | 264 days | 297 days | 333 days |
| 32°F | 315 days | 346 days | 365 days |
| 28°F | 350 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 | 99% |
| 32°F | 80% |
| 28°F | 25% |
| 24°F | 0% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 94523 | 9b | 25 to 30°F | 3 km |
| 94597 | 9b | 25 to 30°F | 7 km |
| 94549 | 9b | 25 to 30°F | 10 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 USC00041967, at 37.9833, -122.0692, elevation 12 m (40 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 4.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Concord Buchanan Field (2 km)
- Martinez Water Plant (5 km)
- Vallejo (17 km)
- Mount Diablo Junction (17 km)
- Berkeley (21 km)
- Oakland Museum (27 km)
- Antioch Pumping Plant #3 (28 km)
- Richmond (28 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.