What does USDA hardiness zone 9b mean in California?

Zone 9b means an average annual extreme minimum winter temperature of 25 to 30 °F — the standard USDA measure of which perennials survive winter. 145 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 9b is the growing season longest?

Agua Dulce runs the longest season on this page at about 364 days; Paynes Creek is shortest at about 96 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 9b?

Using Willows's frost dates (this page's median-season location): start seeds indoors about Jan 1 – Jan 10, then transplant outside about Feb 28 – Mar 7. 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 9b 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 145 locations listed (see the table above for each location's own dates).

USDA zone 9b in California

25 to 30 °F avg. annual extreme minimum · 145 locations in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 9b covers 145 locations across California (average annual extreme minimum 25 to 30 °F): Agua Dulce, CA, Allendale, CA, Alpine, CA, Antioch, CA, Arroyo Grande, CA, Avenal, CA, and 139 more. Average last spring frost across this group ranges January 2 (Agua Dulce) to June 10 (Paynes Creek), and growing seasons run 96–364 days (Paynes Creek to Agua Dulce) — 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 Willows, this group's median-season location.

USDA zone: 9b25 to 30 °F
Last frost range: Jan 2–Jun 10avg, 32°F
First frost range: Sep 13–Dec 30avg, 32°F
Growing season range: 96–364days

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.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Agua Dulce	—	Burbank Valley Pump Plt	Jan 2	Dec 26	364
Allendale	—	Lake Solano	Feb 4	Dec 5	304
Alpine	—	Alpine	Feb 12	Dec 24	317
Antioch	Oakley, Brentwood, Knightsen, Rio Vista, Bethel Island, Isleton	Antioch Pumping Plt #3	Jan 12	Dec 19	343
Arroyo Grande	Morro Bay, Los Ranchos, California Polytechnic State University	San Luis Obispo Poly	Jan 16	Dec 25	349
Avenal	Kettleman	Kettleman City	Feb 19	Nov 29	281
Bakersfield	Rosedale, Arvin, Tarina, Weedpatch, Choctaw Valley, Lakeside, +2 more	Bakersfield Ap	Jan 17	Dec 15	334
Ben Lomond	Brookdale, Davenport	Ben Lomond #4	Mar 25	Nov 11	231
Berry Creek	Chico, Paradise	Paradise	Feb 7	Dec 18	313
Bluewater	—	Parker Resrvoir	frost-free	frost-free	365
Blythe	Cibola	Blythe Ap	Jan 5	Dec 21	347
Bonadelle Ranchos	Madera Acres, Biola	Madera	Feb 18	Nov 27	281
Boonville	Manchester, Point Arena	Ukiah Muni Ap	Mar 5	Nov 21	259
Cabazon	—	Idyllwild Fire Dept	May 16	Oct 24	160
Calipatria	Westmorland	Imperial	Jan 4	Dec 26	360
Calistoga	—	Calistoga	Mar 2	Nov 23	263
Cantua Creek	Westside	Five Points 5 Ssw	Feb 27	Nov 26	271
Carmel Valley	—	Carmel Valley	Feb 20	Dec 8	294
Caspar	Leggett, Manchester, Albion, Cleone, Comptche	Ft Bragg 5 N	Mar 2	Dec 1	272
Catheys Valley	Winton, Cressey, Hornitos, University of California-Merced, Snelling	Merced	Mar 3	Nov 24	263
Chino	—	Chino Ap	Jan 17	Dec 19	335
Coalinga	Huron	Coalinga	Feb 14	Nov 30	292
Cohasset	—	De Sabla	Apr 17	Nov 11	206
Concord	Walnut Creek, Danville, Alamo, Blackhawk, Clayton, Norris Canyon, +2 more	Mt Diablo Junction	Mar 8	Dec 22	282
Concord	Walnut Creek, Pittsburg, Lafayette, Benicia, Pleasant Hill, Rodeo, +3 more	Concord Wwtp	Jan 7	Dec 19	346
Copperopolis	Chinese Camp, La Grange	Sonora	Apr 9	Nov 9	213
Corning	Orland, Artois, Hamilton	Orland	Feb 25	Dec 2	279
Day Valley	Santa Cruz, Scotts Valley, Soquel, Capitola, Paradise Park	Santa Cruz	Jan 29	Dec 13	323
Deer Park	Angwin, Rumsey	Angwin Pacific Union College	Apr 7	Dec 5	245
Descanso	—	Cuyamaca	Apr 19	Oct 27	190
Diablo Grande	Newman, Gustine, Crows Landing	Newman	Feb 26	Nov 29	273
Dixon	University of California-Davis, El Macero	Davis 2 Wsw Exp Farm	Feb 10	Dec 1	295
Drytown	Plymouth, Amador	Sutter Hill Cdf	Mar 4	Dec 11	285
Durham	—	Chico Univ Farm	Mar 4	Nov 17	257
Durham	Palermo, Oroville East, Rackerby, Gridley, Cherokee, Princeton, +2 more	Oroville Muni Ap	Jan 29	Dec 7	317
El Dorado Hills	Diamond Springs, Cameron Park, Shingle Springs, Placerville	Placerville	Mar 31	Nov 21	237
Elmira	—	Vacaville Nut Tree Ap	Feb 18	Nov 28	283
Eureka	Arcata, Loleta, Indianola, Cutten, Fairhaven, Blue Lake, +1 more	Eureka Wfo Woodley Island	Feb 22	Dec 7	293
Fairfield	Green Valley, Suisun	Fairfield	Jan 15	Dec 14	336
Firebaugh	—	Los Banos	Jan 26	Dec 10	322
Fremont	Union	Newark	frost-free	frost-free	365
Fresno	Clovis, Centerville, Reedley, Fowler, Parlier, Sunnyside, +3 more	Fresno Yosemite Intl Ap	Jan 14	Dec 14	337
Garey	—	Twitchell Dam	Feb 4	Dec 4	301
Georgetown	Meadow Vista	Colfax	Apr 3	Nov 24	233
Gilroy	Morgan Hill, San Martin	Gilroy	Feb 24	Nov 27	277
Glen Ellen	Temelec, Yountville, Eldridge	Sonoma	Mar 2	Nov 27	270
Glendora	—	Mt Wilson Cbs	Apr 28	Nov 15	199
Green Valley	—	Fairmont	Apr 6	Nov 29	236
Greenfield	—	King City	Feb 23	Nov 22	271
Guerneville	Forestville, Occidental, Bodega, Valley Ford, Monte Rio, Tomales	Graton	Mar 20	Nov 13	240
Guerneville	Cobb, Healdsburg	Healdsburg	Feb 15	Dec 2	292
Hayward	Castro Valley, Fairview	Hayward Air Terminal	frost-free	frost-free	365
Hercules	El Sobrante	Richmond	frost-free	frost-free	365
Hidden Hills	—	Woodland Hills Pierce College	Jan 24	Dec 15	329
Hollister	San Juan Bautista	Hollister 2	Feb 19	Dec 1	287
Hydesville	Fortuna, Rio Dell, Miranda, Weott, Scotia, Redcrest, +1 more	Scotia	Feb 1	Dec 19	328
Interlaken	Watsonville, Aromas	Watsonville Wtr Wks	Jan 28	Dec 13	324
Jacumba	—	Campo Asos	Apr 29	Nov 1	184
Kentfield	Ross	Kentfield	Jan 16	Dec 18	334
Kenwood	Rutherford, Oakville	Saint Helena	Feb 3	Dec 4	306
Klamath	—	Klamath	Mar 16	Nov 20	252
La Honda	Loma Mar	Skyline Ridge Preserve	Mar 21	Dec 15	275
La Honda	—	Half Moon Bay	Feb 6	Dec 17	328
Lakeside	Ford	Taft	Jan 24	Dec 17	330
Larkfield-Wikiup	—	Santa Rosa	Feb 25	Dec 1	279
Lindsay	Poplar-Cotton Center, Terra Bella, East Porterville, Strathmore	Lindsay	Feb 20	Nov 30	284
Loma Rica	Alta Sierra, Dobbins, Penn Valley, Smartsville	Grass Valley #2	Apr 10	Nov 13	215
Los Alamos	—	Lompoc	Jan 20	Dec 19	335
Lost Hills	Derby Acres, McKittrick, Tupman	Buttonwillow	Feb 9	Nov 26	289
Lucerne	—	Clearlake 4 Se	Apr 10	Nov 6	209
McFarland	—	Wasco	Jan 31	Dec 5	315
McKinleyville	Big Lagoon	Arcata Eureka Ap	Mar 8	Nov 30	262
Menifee	Lake Elsinore, Wildomar, Good Hope	Elsinore	Jan 28	Dec 18	329
Mission Canyon	—	Santa Barbara Muni Ap	Jan 11	Dec 16	342
Modesto	East Oakdale, Riverbank, Del Rio, Riverdale Park, Empire	Modesto City Co Ap	Jan 31	Dec 5	312
Moraga	—	Berkeley	frost-free	frost-free	365
Moreno Valley	Menifee, Murrieta, Perris, Hemet, San Jacinto, Banning, +5 more	San Jacinto	Jan 31	Dec 10	315
Morongo Valley	—	Morongo Valley N	Feb 25	Dec 15	297
Moskowite Corner	—	Markley Cove	Mar 6	Nov 30	266
Mount Laguna	—	Borrego Desert Park	frost-free	frost-free	365
Napa	—	Napa State Hospital	Feb 12	Dec 4	299
Niland	—	Hayfield Pumping Plt	Feb 20	Nov 30	283
Novato	Lucas Valley-Marinwood, Lagunitas-Forest Knolls, Point Reyes Station, Fairfax, San Geronimo, Nicasio	San Rafael Civic Ctr	Jan 11	Dec 21	349
Oak View	—	Ojai	Mar 21	Nov 15	235
Oakland	—	Oakland Metro Intl Ap	Jan 7	Dec 23	356
Orange Cove	East Orosi	Grant Grove	Jun 1	Oct 7	132
Orick	—	Orick Prairie Creek Park	Apr 12	Nov 6	209
Orinda	Moraga	Oakland Museum	frost-free	frost-free	365
Palo Alto	Portola Valley, Atherton, Stanford	Redwood City	Jan 17	Dec 12	333
Palo Alto	Sunnyvale, Mountain View, Cupertino, Los Altos Hills, Los Altos	Moffett Federal Airfield	Jan 6	Dec 23	353
Paskenta	—	Stony Gorge Rsvr	Apr 5	Nov 13	220
Paynes Creek	—	Mineral	Jun 10	Sep 13	96
Philo	—	Ukiah	Mar 19	Nov 20	245
Potrero	—	Campo	Apr 30	Oct 26	174
Prunedale	Elkhorn, Spreckels	Salinas #2	Feb 4	Dec 6	311
Rackerby	—	Strawberry Valley	May 4	Oct 30	174
Ramona	Escondido	Ramona Ap	Mar 19	Nov 23	248
Rancho Calaveras	Clay, Wallace, Ione, Jackson, Campo Seco	Camp Pardee	Jan 22	Dec 17	332
Red Bluff	Flournoy, Los Molinos, Vina	Red Bluff Muni Ap	Feb 22	Nov 29	281
Redway	—	Richardson Gr Sp	Mar 10	Dec 1	271
Richgrove	Jovista	Delano	Jan 31	Dec 8	309
Riverside	Moreno Valley, March ARB, Highgrove	Riverside Muni Ap	Jan 9	Dec 30	362
Roseville	Folsom, Granite Bay, Rocklin, Citrus Heights, Auburn Lake Trails, North Auburn, +4 more	Auburn	Feb 25	Dec 5	286
Sacramento	Rancho Cordova, Wilton, Folsom, Vineyard, Arden-Arcade, Carmichael, +8 more	Sacramento 5 Ese	Jan 12	Dec 16	341
Sacramento	Elk Grove, Walnut Grove, Parkway, Franklin, Clarksburg, Courtland, +1 more	Sacramento Executive Ap	Feb 2	Dec 2	301
Sacramento	Roseville, West Sacramento, Woodland, Rio Linda, Elverta, East Nicolaus, +1 more	Sacramento Metro Ap	Feb 22	Nov 24	277
Sage	—	Hemet	Jan 10	Dec 23	350
Salinas	Gonzales, Spreckels	Salinas Municipal Ap	Jan 29	Dec 10	325
San Bernardino	Redlands, Loma Linda	Redlands	Jan 27	Dec 19	329
San Jose	Saratoga, Los Gatos, Boulder Creek, Campbell, Lexington Hills, Cambrian Park	Los Gatos	Feb 2	Dec 6	310
San Jose	Santa Clara, Cupertino, East Foothills, Fruitdale	San Jose	Jan 12	Dec 22	347
San Jose	Livermore, Morgan Hill, East Foothills	Mt Hamilton	May 3	Nov 18	197
Santa Maria	Nipomo, Casmalia	Santa Maria Public Ap	Feb 4	Dec 13	315
Sea Ranch	Hopland, Anchor Bay, Cloverdale, Kelseyville	Cloverdale	Feb 25	Dec 3	279
Selma	Traver	Hanford 1 S	Feb 7	Dec 1	296
Shasta	—	Whiskeytown Rsvr	Feb 13	Dec 13	304
Shasta Lake	Oak Run	Shasta Dam	Feb 8	Dec 28	322
Shelter Cove	—	Shelter Cove Aviation	frost-free	frost-free	365
Sheridan	Yuba, Plumas Lake, Beale AFB, Olivehurst, Wheatland, Trowbridge, +1 more	Marysville Yuba Co Ap	Feb 11	Nov 30	289
Shingletown	—	Manzanita Lake	Jun 9	Sep 21	102
Smith River	Fort Dick	Crescent City 3 Nnw	Mar 11	Nov 23	256
Soledad	—	Pinnacles Nm	Apr 23	Nov 3	189
Stockton	Manteca, Lathrop, Linden, Ripon, French Camp, Garden Acres, +4 more	Stockton Metro Ap	Feb 6	Dec 1	304
Stockton	Lockeford, Herald, Collierville, Woodbridge, Morada, Victor, +2 more	Lodi	Feb 9	Dec 5	301
Sunol	Livermore, Pleasanton, San Ramon, Dublin	Livermore	Feb 15	Dec 2	292
Tahoe Vista	—	Tahoe City	Jun 9	Sep 25	108
Temecula	Valley Center, Lake Riverside	Palomar Mtn Obsy	Apr 29	Nov 18	201
Temelec	Petaluma Center, Sonoma State University	Petaluma Ap	Feb 28	Nov 25	271
Three Rivers	Woodlake, Lemon Cove, Lindcove	Lemon Cove	Feb 5	Dec 8	307
Three Rivers	Sequoia Crest	Three Rivers Edison Ph 1	Mar 16	Nov 26	249
Timber Cove	—	Ft Ross	Feb 26	Dec 27	310
Tracy	Westley, Grayson	Tracy Carbona	Feb 25	Nov 26	272
Tracy	Byron, Mountain House, Terminous	Tracy Pumping Plt	Jan 19	Dec 10	330
Turlock	Delhi, Ballico, Waterford, Hughson, Keyes, Hickman, +1 more	Turlock #2	Jan 6	Dec 20	351
Twentynine Palms	—	Twentynine Palms	Jan 24	Dec 10	321
Vallejo	American Canyon	Napa Co Ap	Mar 5	Nov 21	256
Visalia	Dinuba, Goshen, Farmersville, Ivanhoe, Cutler, Matheny, +2 more	Visalia	Jan 23	Dec 13	328
Whitewater	—	Palm Springs Rgnl Ap	frost-free	frost-free	365
Williams	Colusa, Live Oak, Sutter, Rumsey, Grimes, Maxwell, +2 more	Colusa 2 Ssw	Feb 14	Dec 1	293
Willows *	—	Willows 6 W	Feb 21	Dec 6	289
Winters	—	Winters	Feb 18	Nov 30	284
Woodland	Dunnigan, Esparto, Monument Hills, Robbins, Madison, Yolo	Woodland 1 Wnw	Feb 7	Dec 5	301
Woody	Ducor	Glennville	May 11	Oct 17	155
Yosemite Lakes	Millerton, Friant, Fort Washington	Friant Government Camp	Mar 9	Dec 1	262
Yucaipa	—	Big Bear Lake	May 27	Oct 4	131

* Willows 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 (Willows, representative)

Computed from Willows's average frost dates — the median-season location in this Californiazone 9b 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).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Willows (California, zone 9b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Jan 1 – Jan 10	Feb 28 – Mar 7	Apr 29 – May 19	—	matures comfortably
Pepper	Very tender	Jan 1	Mar 7 – Mar 14	May 6 – Jun 5	—	matures comfortably
Cucumber	Tender	Jan 24 – Jan 31	Feb 28 – Mar 7	Apr 19 – May 9	—	matures comfortably
Summer squash / zucchini	Tender	—	Feb 28 – Mar 7	Apr 14 – Apr 29	—	matures comfortably
Bush bean	Tender	—	Feb 28 – Mar 7	Apr 19 – Apr 29	Oct 7 – Oct 17	matures comfortably
Sweet corn	Tender	—	Feb 21 – Mar 7	Apr 22 – May 22	—	matures comfortably
Basil	Very tender	Jan 10 – Jan 24	Feb 28 – Mar 7	Mar 30 – Apr 14	—	matures comfortably
Lettuce	Half-hardy	Jan 10 – Jan 24	Jan 24 – Feb 7	Mar 10 – Mar 25	Sep 23 – Oct 8	matures comfortably
Pea	Hardy	—	Jan 10 – Jan 24	Mar 6 – Mar 21	Sep 13 – Sep 28	matures comfortably
Spinach	Hardy	—	Jan 10 – Jan 24	Feb 19 – Mar 1	Oct 3 – Oct 13	matures comfortably
Carrot	Half-hardy	—	Jan 31 – Feb 7	Apr 1 – Apr 21	Sep 3 – Sep 23	matures comfortably
Broccoli	Half-hardy	Jan 1 – Jan 10	Jan 24 – Feb 7	Mar 20 – Apr 9	Sep 8 – Sep 28	matures comfortably

Which crops fit this growing season

Using Willows's own 289-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 (Willows)

From NOAA's 1991–2020 Climate Normals at station USC00049699. 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.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Willows.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	Apr 2	Apr 25	Nov 23	Dec 7	233
32°F (freeze)	Feb 21	Apr 9	Dec 6	Dec 29	289
28°F	Jan 5	Feb 24	Dec 18	Jan 27	348
24°F	Dec 29	Jan 20	Dec 25	Jan 18	365

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 145 locations is 4,181; Willows's own reading is shown below.

Annual growing degree days for Willows (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	5,247	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	8,677	cool-season crops (brassicas, greens)

Hardiness zone 9b in California

Zone 9b means an average annual extreme minimum winter temperature of about 25 to 30 °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, 9a, 10a, 10b, 11a.

Explore zone 9b in other states at zone 9b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 9b mean in California?: Zone 9b means an average annual extreme minimum winter temperature of 25 to 30 °F — the standard USDA measure of which perennials survive winter. 145 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 9b is the growing season longest?: Agua Dulce runs the longest season on this page at about 364 days; Paynes Creek is shortest at about 96 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 9b?: Using Willows's frost dates (this page's median-season location): start seeds indoors about Jan 1 – Jan 10, then transplant outside about Feb 28 – Mar 7. 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 9b 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 145 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.