California climate zones for Title 24.
California is divided into 16 building climate zones by the California Energy Commission. Your zone is set by ZIP code and it decides what your project has to hit. Find yours, then read what it means for the design.
Schematic: nodes are placed for legibility, not survey accuracy. Zone boundaries follow ZIP code lines.
Enter a city or ZIP code, or click any numbered node on the map, and we'll tell you the zone, what drives the design there, and where projects usually lose margin.
Zone assignment is set by the California Energy Commission and follows ZIP code boundaries. A handful of cities straddle two zones. If yours is one of them we will confirm it from the address for free.
The whole table
Reference city is the CEC weather station the compliance model runs against, which is not necessarily the biggest city in the zone.
| Zone | Name | CEC reference city | Design driver | Region |
|---|---|---|---|---|
| CZ 1 | North Coast | Arcata | Heating | Del Norte, Humboldt and coastal Mendocino |
| CZ 2 | North Bay and Wine Country | Santa Rosa | Mixed | Sonoma, Napa, Marin, inland Mendocino, the Solano coast |
| CZ 3 | San Francisco Bay Coastal | Oakland | Heating | San Francisco, the Alameda and San Mateo coast, Santa Cruz, Monterey |
| CZ 4 | Santa Clara Valley | San Jose | Mixed | San Jose, the South Bay, Gilroy, Hollister, Paso Robles |
| CZ 5 | Central Coast | Santa Maria | Heating | San Luis Obispo, Santa Barbara, Lompoc, Pismo, Goleta |
| CZ 6 | Los Angeles and Orange County Coastal | Torrance | Cooling | Santa Monica, Long Beach, the South Bay, coastal Orange County, Ventura |
| CZ 7 | San Diego Coastal | San Diego | Cooling | San Diego, Chula Vista, Carlsbad, Oceanside, Encinitas, La Mesa |
| CZ 8 | Inland Orange County | Fullerton | Cooling | Anaheim, Irvine, Fullerton, Garden Grove, Downey |
| CZ 9 | LA Basin and San Fernando Valley | Burbank | Cooling | Pasadena, Burbank, Glendale, the Valley, Santa Clarita, the San Gabriel Valley |
| CZ 10 | Inland Empire and Inland San Diego | Riverside | Cooling | Riverside, San Bernardino, Corona, Temecula, Escondido, Fontana |
| CZ 11 | Northern Sacramento Valley | Red Bluff | Cooling | Redding, Chico, Yuba City, Marysville, Oroville |
| CZ 12 | Sacramento Valley and Delta | Sacramento | Cooling | Sacramento, Stockton, Modesto, Elk Grove, Roseville, Livermore, Concord |
| CZ 13 | San Joaquin Valley | Fresno | Cooling | Fresno, Bakersfield, Visalia, Clovis, Madera, Hanford, Tulare |
| CZ 14 | High Desert | Palmdale | Both | Lancaster, Palmdale, Victorville, Barstow, Yucca Valley, Ridgecrest |
| CZ 15 | Low Desert | Palm Springs | Cooling | Palm Springs, Palm Desert, Indio, La Quinta, El Centro, Blythe |
| CZ 16 | Mountains | Blue Canyon | Heating | Tahoe, Truckee, Mammoth, Big Bear, Bishop and the Sierra communities |
What each zone does to your design.
Same code, sixteen different problems. This is where the margin comes from, and where it goes.
North Coast
Reference city: Arcata
Cool, wet and famously mild. Almost no cooling load, so the whole compliance question is heating and how tight the envelope is.
Watch out for: Wall and attic insulation plus air-tightness carry the margin. Cooling equipment is often not required at all.
Del Norte, Humboldt and coastal Mendocino
Price a Zone 1 project →North Bay and Wine Country
Reference city: Santa Rosa
Mild coastal-influenced climate with real summer heat inland. A middle-of-the-road zone where the standard package usually works.
Watch out for: Whole-house fans and good shading earn easy margin. Watch west-facing glazing in the valleys.
Sonoma, Napa, Marin, inland Mendocino, the Solano coast
Price a Zone 2 project →San Francisco Bay Coastal
Reference city: Oakland
California's gentlest climate. Small heating load, negligible cooling. Compliance is usually straightforward.
Watch out for: Heat pump water heating is an easy win here. Cooling rarely drives the design.
San Francisco, the Alameda and San Mateo coast, Santa Cruz, Monterey
Price a Zone 3 project →Santa Clara Valley
Reference city: San Jose
Warm-summer Mediterranean, one ridge inland from the fog. Cooling starts to matter without dominating.
Watch out for: West and south glazing area is the usual sticking point. Overhangs pay for themselves.
San Jose, the South Bay, Gilroy, Hollister, Paso Robles
Price a Zone 4 project →Central Coast
Reference city: Santa Maria
Marine layer keeps summers cool and winters soft. One of the easiest zones to pass.
Watch out for: Low loads mean small equipment. Don't oversize the HVAC, because it costs you on the performance run.
San Luis Obispo, Santa Barbara, Lompoc, Pismo, Goleta
Price a Zone 5 project →Los Angeles and Orange County Coastal
Reference city: Torrance
Coastal Southern California. Mild all year, modest cooling, very little heating.
Watch out for: Glazing SHGC does most of the work. Heating equipment is nearly incidental.
Santa Monica, Long Beach, the South Bay, coastal Orange County, Ventura
Price a Zone 6 project →San Diego Coastal
Reference city: San Diego
The mildest climate in the state's largest southern metro. Both loads are small, and the prescriptive package is usually comfortable.
Watch out for: Ducts in conditioned space and a good SHGC are typically all the margin a project needs.
San Diego, Chula Vista, Carlsbad, Oceanside, Encinitas, La Mesa
Price a Zone 7 project →Inland Orange County
Reference city: Fullerton
One ridge back from the coast and noticeably hotter. Cooling is now the design driver.
Watch out for: Cool roofs and duct location start to matter. West glazing needs shading or a low SHGC.
Anaheim, Irvine, Fullerton, Garden Grove, Downey
Price a Zone 8 project →LA Basin and San Fernando Valley
Reference city: Burbank
Hot dry summers, cool nights, mild winters. The busiest residential zone in California.
Watch out for: Attic and duct performance dominate. Radiant barrier and a cool roof are cheap margin here.
Pasadena, Burbank, Glendale, the Valley, Santa Clarita, the San Gabriel Valley
Price a Zone 9 project →Inland Empire and Inland San Diego
Reference city: Riverside
Hot summers and real winter nights. High volume, and cooling loads big enough that design choices show up in the results.
Watch out for: This is where projects fail on glazing. Keep west-facing window area honest and specify low SHGC.
Riverside, San Bernardino, Corona, Temecula, Escondido, Fontana
Price a Zone 10 project →Northern Sacramento Valley
Reference city: Red Bluff
Genuinely hot valley summers with cold snaps in winter. Both loads are significant.
Watch out for: Duct leakage and attic insulation are the two biggest levers. Field verification is nearly always in play.
Redding, Chico, Yuba City, Marysville, Oroville
Price a Zone 11 project →Sacramento Valley and Delta
Reference city: Sacramento
Hot dry summers, foggy cool winters. The state's second-largest residential market by volume.
Watch out for: Whole-house fans are a strong performance-method credit. Duct location matters a great deal.
Sacramento, Stockton, Modesto, Elk Grove, Roseville, Livermore, Concord
Price a Zone 12 project →San Joaquin Valley
Reference city: Fresno
The Central Valley proper. A long, severe cooling season and a real heating season behind it.
Watch out for: Cool roof, tight ducts, and a serious look at glazing. Margins are thinner here than on the coast.
Fresno, Bakersfield, Visalia, Clovis, Madera, Hanford, Tulare
Price a Zone 13 project →High Desert
Reference city: Palmdale
Desert extremes in both directions: brutal summers and freezing winter nights.
Watch out for: Envelope first. The swing between seasons punishes weak insulation twice over.
Lancaster, Palmdale, Victorville, Barstow, Yucca Valley, Ridgecrest
Price a Zone 14 project →Low Desert
Reference city: Palm Springs
The hardest cooling climate in California. Every square foot of west-facing glass costs you.
Watch out for: The toughest zone to pass. Expect a performance run, low-SHGC glazing, and ducts in conditioned space.
Palm Springs, Palm Desert, Indio, La Quinta, El Centro, Blythe
Price a Zone 15 project →Mountains
Reference city: Blue Canyon
California's cold climate. Heating dominates completely and snow load shapes the assemblies.
Watch out for: Insulation levels and window U-factor are everything. High-performance glazing is not optional.
Tahoe, Truckee, Mammoth, Big Bear, Bishop and the Sierra communities
Price a Zone 16 project →Zone boundaries follow ZIP codes, not city limits
Since the 2013 Standards, every California ZIP code sits entirely inside one climate zone. Before that, boundaries could cut through a ZIP and the answer depended on which side of a street you were on.
This matters most at the edges. The Los Angeles basin has Zones 6, 8 and 9 within a few miles of each other, and San Diego County runs from Zone 7 on the coast to Zone 10 inland and Zone 15 in the desert. Getting it wrong doesn't produce an error; it produces a report run against the wrong weather file.
The lookup on this page
Covers California's larger cities and metro ZIP ranges, enough for the great majority of projects. It's a fast answer, not a legal determination.
For the authoritative source, the California Energy Commission publishes the full ZIP-to-zone list, and zone assignment is set out in Reference Joint Appendix JA2.
CEC official ZIP list →Or just send us the address. We'll confirm the zone free, whether or not you end up hiring us.
About climate zones
How do we find our California climate zone?
Your zone is set by the project's ZIP code. Use the finder on this page, or check the California Energy Commission's official ZIP code list. Since the 2013 Standards a given ZIP code always sits entirely inside one zone, so there are no more split ZIPs.
Why does the climate zone matter so much?
It sets the weather data the compliance model runs against, and therefore the whole energy budget. The same house that passes comfortably in Zone 3 can fail in Zone 15 without a single drawing changing.
Which climate zone is hardest to pass?
Zone 15, the low desert around Palm Springs and El Centro. Cooling loads are extreme and west-facing glazing is punishing. Zone 16, the mountains, is the hardest on the heating side. Zones 3, 5 and 7 are the most forgiving.
My city appears in two zones. Which one applies?
The one your ZIP code sits in. A few larger cities span more than one ZIP-defined zone. Send us the project address and we'll confirm it at no charge. It takes a minute and it's not worth guessing.
Know your zone. Now get your number.
The calculator prices your project in the open, and the climate zone is already baked into how we model it.
Or call (909) 914-0305 and you'll get the engineer, not a receptionist.