Frost dates in USDA zone 9b (25 to 30°F)
USDA zone 9b covers places whose coldest winter night averages 25 to 30°F. Across the 277 NOAA weather stations in zone 9b, the median last spring frost is Feb 4, but it ranges from Jan 14 to Mar 4 for most stations. Enter your ZIP for your local date.
- Feb 4Median last spring frostmost stations Jan 14–Mar 4
- Dec 13Median first fall frost50% chance of 32°F by this date
- 312 daysMedian growing seasonbetween 32°F freezes
- 2,085ZIP codes in zone 9b25 to 30°F average coldest night
- 277Stations with frost datesof 278 NOAA stations matched
Earliest and latest last-frost stations in zone 9b
| Station | Last spring frost | First fall frost |
|---|---|---|
| San Jose, CA | Jan 2 | Dec 25 |
| Iron Mountain, CA | Jan 3 | Dec 31 |
| Bullhead City, AZ | Jan 4 | Dec 23 |
| Ehrenberg 2 E, AZ | Jan 4 | Dec 19 |
| Blythe Airport, CA | Jan 5 | Dec 21 |
| Laughlin, NV | Jan 5 | Dec 24 |
| Fountain Hills, AZ | Jan 6 | Dec 28 |
| Moffett Federal Airfield, CA | Jan 6 | Dec 23 |
| Needles Airport, CA | Jan 6 | Jan 2 |
| Turlock #2, CA | Jan 6 | Dec 20 |
| Station | Last spring frost | First fall frost |
|---|---|---|
| Mount Hamilton, CA | May 3 | Nov 18 |
| Palomar Mountain Obsy, CA | Apr 29 | Nov 18 |
| Pinnacles National Monument, CA | Apr 23 | Nov 3 |
| Groveland 2, CA | Apr 22 | Nov 2 |
| Cuyamaca, CA | Apr 19 | Oct 27 |
| Paicines 4 W, CA | Apr 14 | Nov 2 |
| Orick Prairie Creek Park, CA | Apr 12 | Nov 6 |
| Grass Valley #2, CA | Apr 10 | Nov 13 |
| Angwin Pacific Union College, CA | Apr 7 | Dec 5 |
| Dobbins 1 S, CA | Apr 1 | Nov 17 |
Zone 9b by state
| State | Stations | Median last frost | Median first frost |
|---|---|---|---|
| Alabama | 1 | Jan 31 | Jan 6 |
| Arizona | 33 | Jan 23 | Dec 15 |
| California | 123 | Feb 9 | Dec 5 |
| Florida | 37 | Feb 1 | Jan 5 |
| Louisiana | 19 | Feb 5 | Dec 17 |
| Nevada | 6 | Jan 22 | Dec 14 |
| Oregon | 5 | Feb 17 | Dec 3 |
| Texas | 54 | Feb 4 | Dec 12 |
Neighboring zones
How these numbers are made
Each ZIP code gets one zone from the USDA-ARS / PRISM 2023 ZIP tables, which use the map’s 1991–2020 average of the coldest winter night of each year. A ZIP code can span more than one zone, and USDA’s own lookup works by ZIP or address. Each NOAA station is assigned the most common zone among the closest ZIP codes listed on its station page (a tie goes to the zone of the closest of those ZIPs). Frost dates are NOAA’s 50%-probability (median) 32°F dates for each station, the same values shown on the station pages. Zone figures are the median, 10th and 90th percentile across stations; a first fall frost in January to June is counted in the following year.
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.
Sources
- 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.
- 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.
- 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.