USDA zone 9a in California
USDA plant hardiness zone 9a covers 94 locations across California (average annual extreme minimum 20 to 25 °F): Acton, CA, Aguanga, CA, Angels, CA, Angwin, CA, Atascadero, CA, Auberry, CA, and 88 more. Average last spring frost across this group ranges January 1 (Furnace Creek) to June 9 (Manton), and growing seasons run 102–351 days (Manton to Hilmar-Irwin) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every California location's own frost dates; the printable planting calendar uses Redding, this group's median-season location.
- USDA zone
- 9a20 to 25 °F
- Last frost range
- Jan 1–Jun 9avg, 32°F
- First frost range
- Sep 19–Dec 28avg, 32°F
- Growing season range
- 102–351days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Acton | Desert View Highlands | Palmdale | Mar 10 | Nov 19 | 248 |
| Aguanga | — | Palomar Mtn Obsy | Apr 29 | Nov 18 | 201 |
| Angels | — | New Melones Dam Hq | Feb 20 | Dec 11 | 290 |
| Angwin | Tancred | Angwin Pacific Union College | Apr 7 | Dec 5 | 245 |
| Atascadero | — | San Luis Obispo Poly | Jan 16 | Dec 25 | 349 |
| Auberry | North Fork, Coarsegold, Bass Lake | Auberry 2 Nw | Mar 25 | Dec 3 | 253 |
| Baker | — | Baker | Feb 14 | Nov 27 | 287 |
| Barstow | Lenwood | Barstow | Feb 22 | Nov 23 | 271 |
| Ben Lomond | — | Ben Lomond #4 | Mar 25 | Nov 11 | 231 |
| Benbow | Leggett, Garberville, Alderpoint, Phillipsville | Richardson Gr Sp | Mar 10 | Dec 1 | 271 |
| Boulevard | — | Campo Asos | Apr 29 | Nov 1 | 184 |
| Brooktrails | Potter Valley, Redwood Valley, Upper Lake | Potter Valley Powerhouse | Apr 8 | Nov 6 | 211 |
| Buttonwillow | Smith Corner | Buttonwillow | Feb 9 | Nov 26 | 289 |
| Camino | River Pines | Placerville | Mar 31 | Nov 21 | 237 |
| Campo | Potrero | Campo | Apr 30 | Oct 26 | 174 |
| Challenge-Brownsville | Forbestown, Pike, Clipper Mills, Camptonville | Strawberry Valley | May 4 | Oct 30 | 174 |
| Chico | — | Paradise | Feb 7 | Dec 18 | 313 |
| Chowchilla | Mendota, Kerman, Biola, Tranquillity, La Vina | Madera | Feb 18 | Nov 27 | 281 |
| Clearlake | Spring Valley, Lower Lake | Clearlake 4 Se | Apr 10 | Nov 6 | 209 |
| Columbia | Murphys, Vallecito, East Sonora | Sonora | Apr 9 | Nov 9 | 213 |
| Corcoran | Pixley, Tipton, Alpaugh | Corcoran Irrig Dist | Feb 15 | Nov 27 | 285 |
| Covelo | Laytonville | Covelo | Apr 23 | Oct 19 | 179 |
| Dobbins | — | Dobbins 1 S | Apr 1 | Nov 17 | 229 |
| Durham | — | Oroville Muni Ap | Jan 29 | Dec 7 | 317 |
| Earlimart | — | Delano | Jan 31 | Dec 8 | 309 |
| El Paso de Robles (Paso Robles) | Templeton | Paso Robles | Mar 15 | Nov 10 | 238 |
| Elk Creek | — | Stony Gorge Rsvr | Apr 5 | Nov 13 | 220 |
| Forest Ranch | — | De Sabla | Apr 17 | Nov 11 | 206 |
| Foresthill | Meadow Vista, Colfax, Dutch Flat | Colfax | Apr 3 | Nov 24 | 233 |
| Fort Irwin | Yermo | Barstow Daggett Ap | Feb 19 | Nov 26 | 279 |
| French Gulch | Lakehead | Shasta Dam | Feb 8 | Dec 28 | 322 |
| French Gulch | Ono | Whiskeytown Rsvr | Feb 13 | Dec 13 | 304 |
| Furnace Creek | — | Death Valley Np | Jan 1 | Dec 19 | 350 |
| Georgetown | — | Georgetown Rs | Apr 12 | Nov 21 | 221 |
| Grass Valley | Washington, Dutch Flat | Nevada City | Apr 14 | Nov 20 | 218 |
| Grizzly Flats | — | Pacific House | Apr 26 | Nov 2 | 191 |
| Guinda | — | Woodland 1 Wnw | Feb 7 | Dec 5 | 301 |
| Hidden Valley Lake | — | Calistoga | Mar 2 | Nov 23 | 263 |
| Hilmar-Irwin | Livingston | Turlock #2 | Jan 6 | Dec 20 | 351 |
| Homestead Valley | — | Johnson Valley | Mar 1 | Nov 29 | 271 |
| Johannesburg | Randsburg | Randsburg | Mar 19 | Nov 25 | 251 |
| Joshua Tree | — | Joshua Tree | Feb 28 | Dec 1 | 273 |
| Julian | — | Borrego Desert Park | frost-free | frost-free | 365 |
| Julian | — | Henshaw Dam | Apr 18 | Oct 26 | 189 |
| Keene | — | Tehachapi 4 Se | Apr 28 | Oct 26 | 183 |
| Lake Hughes | — | Fairmont | Apr 6 | Nov 29 | 236 |
| Lake Isabella | McClenney Tract | Glennville | May 11 | Oct 17 | 155 |
| Laytonville | — | Ft Bragg 5 N | Mar 2 | Dec 1 | 272 |
| Lemoore | Laton, Armona, Stratford, Home Garden | Hanford 1 S | Feb 7 | Dec 1 | 296 |
| Lemoore Station | Caruthers, Lanare | Lemoore Reeves Nas | Feb 24 | Nov 22 | 265 |
| Lincoln | — | Auburn | Feb 25 | Dec 5 | 286 |
| Littlerock | — | Mt Wilson Cbs | Apr 28 | Nov 15 | 199 |
| Lockwood | King, Fort Hunter Liggett, San Lucas | King City | Feb 23 | Nov 22 | 271 |
| Lodoga | — | East Park Rsvr | Apr 6 | Nov 10 | 219 |
| Los Banos | Dos Palos Y, South Dos Palos | Los Banos | Jan 26 | Dec 10 | 322 |
| Lucerne | — | Ukiah Muni Ap | Mar 5 | Nov 21 | 259 |
| Mad River | Phillipsville | Scotia | Feb 1 | Dec 19 | 328 |
| Manton | Whitmore | Manzanita Lake | Jun 9 | Sep 21 | 102 |
| Merced | McSwain, El Nido, Planada, Le Grand, University of California-Merced | Merced | Mar 3 | Nov 24 | 263 |
| Midpines | Mariposa, Nipinnawasee, Fish Camp | So Entrance Yosemite Np | May 24 | Oct 10 | 137 |
| Montgomery Creek | Round Mountain | Hat Creek | May 29 | Sep 19 | 113 |
| Morongo Valley | — | Morongo Valley N | Feb 25 | Dec 15 | 297 |
| Mount Hermon | — | Santa Cruz | Jan 29 | Dec 13 | 323 |
| New Cuyama | — | New Cuyama Fire Stn | Apr 15 | Nov 4 | 201 |
| Oak Shores | — | Hearst Castle | frost-free | frost-free | 365 |
| Pine Grove | Lockwood, Amador, River Pines | Sutter Hill Cdf | Mar 4 | Dec 11 | 285 |
| Platina | — | Weaverville | May 3 | Oct 11 | 159 |
| Proberta | Gerber, Tehama | Red Bluff Muni Ap | Feb 22 | Nov 29 | 281 |
| Rail Road Flat | San Andreas, Wilseyville, Amador Pines, Sheep Ranch | Calaveras Big Trees | May 7 | Oct 28 | 169 |
| Raisin | — | Fresno Yosemite Intl Ap | Jan 14 | Dec 14 | 337 |
| Redding * | Cottonwood, Millville, Anderson, Oak Run | Redding Muni Ap | Mar 3 | Nov 21 | 261 |
| Rohnert Park | Cotati | Petaluma Ap | Feb 28 | Nov 25 | 271 |
| Rough and Ready | — | Grass Valley #2 | Apr 10 | Nov 13 | 215 |
| Salyer | — | Big Bar 4 E | Apr 16 | Oct 31 | 197 |
| San Ardo | — | Priest Valley | May 8 | Oct 22 | 165 |
| Santa Rosa | Rohnert Park | Santa Rosa | Feb 25 | Dec 1 | 279 |
| Searles Valley | — | Trona | Feb 15 | Nov 28 | 285 |
| Sebastopol | Graton | Graton | Mar 20 | Nov 13 | 240 |
| Shaver Lake | — | Balch Pwr House | Feb 23 | Dec 12 | 294 |
| Soledad | — | Pinnacles Nm | Apr 23 | Nov 3 | 189 |
| Solvang | — | Cachuma Lake | Apr 11 | Nov 8 | 209 |
| Squaw Valley | Wilsonia | Grant Grove | Jun 1 | Oct 7 | 132 |
| Stevinson | — | Newman | Feb 26 | Nov 29 | 273 |
| Stockton | — | Stockton Metro Ap | Feb 6 | Dec 1 | 304 |
| Tecopa | — | Pahrump 4 Nw | Mar 29 | Nov 3 | 218 |
| Tres Pinos | — | Hollister 2 | Feb 19 | Dec 1 | 287 |
| Ukiah | — | Ukiah | Mar 19 | Nov 20 | 245 |
| Wasco | — | Wasco | Jan 31 | Dec 5 | 315 |
| Weitchpec | — | Orleans | Mar 12 | Nov 26 | 262 |
| Weldon | Onyx | S Lake Fs | Apr 5 | Nov 3 | 212 |
| Westside | San Joaquin | Five Points 5 Ssw | Feb 27 | Nov 26 | 271 |
| Willow Creek | — | Arcata Eureka Ap | Mar 8 | Nov 30 | 262 |
| Windsor | Larkfield-Wikiup, Fulton | Santa Rosa Sonoma Co Ap | Mar 2 | Nov 20 | 262 |
| Yucca Valley | — | Yucca Valley | Mar 14 | Nov 28 | 255 |
* Redding is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Redding, representative)
Computed from Redding's average frost dates — the median-season location in this Californiazone 9a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Jan 6 – Jan 20 | Mar 10 – Mar 17 | May 9 – May 29 | — | matures comfortably |
| Pepper | Very tender | Jan 1 – Jan 6 | Mar 17 – Mar 24 | May 16 – Jun 15 | — | matures comfortably |
| Cucumber | Tender | Feb 3 – Feb 10 | Mar 10 – Mar 17 | Apr 29 – May 19 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Mar 10 – Mar 17 | Apr 24 – May 9 | — | matures comfortably |
| Bush bean | Tender | — | Mar 10 – Mar 17 | Apr 29 – May 9 | Sep 22 – Oct 2 | matures comfortably |
| Sweet corn | Tender | — | Mar 3 – Mar 17 | May 2 – Jun 1 | — | matures comfortably |
| Basil | Very tender | Jan 20 – Feb 3 | Mar 10 – Mar 17 | Apr 9 – Apr 24 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 20 – Feb 3 | Feb 3 – Feb 17 | Mar 20 – Apr 4 | Sep 8 – Sep 23 | matures comfortably |
| Pea | Hardy | — | Jan 20 – Feb 3 | Mar 16 – Mar 31 | Aug 29 – Sep 13 | matures comfortably |
| Spinach | Hardy | — | Jan 20 – Feb 3 | Mar 1 – Mar 11 | Sep 18 – Sep 28 | matures comfortably |
| Carrot | Half-hardy | — | Feb 10 – Feb 17 | Apr 11 – May 1 | Aug 19 – Sep 8 | matures comfortably |
| Broccoli | Half-hardy | Jan 6 – Jan 20 | Feb 3 – Feb 17 | Mar 30 – Apr 19 | Aug 24 – Sep 13 | matures comfortably |
Which crops fit this growing season
Using Redding's own 261-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Redding)
From NOAA's 1991–2020 Climate Normals at station USW00024257. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Apr 7 | Apr 26 | Nov 9 | Nov 22 | 215 |
| 32°F (freeze) | Mar 3 | Apr 9 | Nov 21 | Dec 7 | 261 |
| 28°F | Jan 27 | Mar 1 | Dec 7 | Jan 5 | 316 |
| 24°F | Jan 1 | Feb 2 | Dec 18 | Jan 22 | 362 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 94 locations is 3,991; Redding's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 5,311 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 8,598 | cool-season crops (brassicas, greens) |
Hardiness zone 9a in California
Zone 9a means an average annual extreme minimum winter temperature of about 20 to 25 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. California spans 12 hardiness zones in this dataset — see all California locations for the full range, including zones5b, 6a, 6b, 7a, 7b, 8a, 8b, 9b, 10a, 10b, 11a.
Explore zone 9a in other states at zone 9a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 9a mean in California?
- Zone 9a means an average annual extreme minimum winter temperature of 20 to 25 °F — the standard USDA measure of which perennials survive winter. 94 locations in California fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in California's zone 9a is the growing season longest?
- Hilmar-Irwin runs the longest season on this page at about 351 days; Manton is shortest at about 102 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in California's zone 9a?
- Using Redding's frost dates (this page's median-season location): start seeds indoors about Jan 6 – Jan 20, then transplant outside about Mar 10 – Mar 17. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in California's zone 9a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 94 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.