I'd recommend getting the Sunset Western Garden Book. It describes and maps the Sunset zones and describes the types of plants that grow in each zone.

Southern California near the coast doesn't get too hot!

kawaiineko, you might also want to look at Plant Maps' Heat Zone map for California, which shows how many days per year are likely to be above 86 degrees:

http://www.plantmaps.com/interactive-california-heat-zones-map.php

When I was 12, we moved from Fremont to Menlo Park -- from about 4 miles east of the Bay to about 5 miles west of the Bay, and a total distance of about 14 miles -- and couldn't understand why the summer was so hot in Menlo Park. Now I see that we moved from Zone 1 (averaging no more than 1 day above 86* per year) to zone 5 (averaging between 31 and 45 days above 86* per year)!

[You can also put in a zip code for somewhere in a different state and see a Heat Zone map for that state.

Note the list of Plant Maps' other maps with different information in the right hand margin.]

I'm under the impression that these Heat Zone maps are simply a non-copyrighted version of the American Horticultural Society's Plant Heat Zone Map, which is illegible online, but they will happily sell you a legible printed map. I assume both groups generated the maps from non-copyrighted government info.
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USDA's Plant Hardiness Zone shows the average low temperature (within a 5* F. range) -- and that's all it indicates. USDA zone info is really only good for knowing what plants should survive winter cold.

For instance, both San Francisco much of middle Florida are both 9b.

9b in San Francisco means mild summer weather (my dad swore June was the coldest month of the year and frequently took his coat to work), foggy, and extremely changeable. It's difficult to ripen tomatoes because sunlight and heat are both sometimes inadequate.

9b in Florida, on the other hand, is horribly hot and humid and includes some of the best commercial tomato-growing areas in the state -- but you can't really grow tomatoes outdoors in the summer in Florida, because it's too hot for successful pollination and fruitset, and the plant itself is overly stressed.

http://planthardiness.ars.usda.gov/PHZMWeb/

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Sunset's system actually covers the entire U.S., not simply California. It gives a more detailed description of the type of weather year round -- but the degree of detail it gives varies from place to place. For some places it sounds very helpful. But when I look at the map, my zone 36 includes pretty much the entire Appalachian region between southern Pennsylvania and about 30 miles north of Atlanta (an area extending more than 400 miles).

"Growing season: May to late Oct. Thanks to greater elevation, summers are cooler and less humid, winters colder (0 degrees to -20 degrees F/-18 degrees to -29 degrees C) than in adjacent, lower zones. Rain comes all year (heaviest in spring). Late frosts are common."

It may be accurate, but it's too general -- and it won't tell you whether your new plants will freeze or not!
http://www.sunset.com/garden/climate-zones/

It sounds like you want the mythical perfect microclimate. Generally speaking you either get good chill hours or good subtropical, but not both.

If you don't want frosts in winter, or only a few, light ones, you're looking for a USDA Zone 9b/10a microclimate, not 8a/8b. That typically means you'll need to look for Sunset zones 15/16/17 here in northern California, although Sunset zones 14/15 can easily dip down to the low 20's°F in cold winters. That means bananas and citrus need protection, or they will get damaged, and don't expect to get edible bananas in northern California without some real effort.

I like to grow zone 10 plants, so my preference is for warmer parts of Sunset zone 17, or anywhere with a Sunset zone 16 climate. This typically means within sight of bay or ocean, and property is expensive. Rarely too hot, however, summers in these zones are generally in the 70's°F to low 80's°F at the hottest, possibly a week at most of 90's°F during the year.

It looks like this is what you're looking for (see below). I wonder if Paso Robles would be in this area?

ZONE 7: California’s Gray Pine Belt, Oregon’s Rogue River Valley, and Southern California mountains

Zone 7 encompasses several thousand square miles west of the Sierra Nevada and Cascade ranges, and in the mountains that separate the Southern California coast from interior deserts. Because of the influence of latitude, this climate lies mostly at low elevations in Oregon’s Rogue Valley, middle elevations around California’s Central Valley, and at middle to higher elevations farther south. Gray pines define the heart of Zone 7 around the Central Valley, but more adaptable incense cedars replace them farther north and south.

Hot summers and mild but pronounced winters give Zone 7 sharply defined seasons without severe winter cold or enervating humidity. The climate pleases plants that require a marked seasonal pattern to do well��"flower bulbs, peonies, lilacs, and flowering cherries, for example. Deciduous fruit trees do well also; the region is noted for its pears, apples, peaches, and cherries.

Gardeners in a few spots around the San Francisco Bay will be surprised to find their gardens mapped in Zone 7. These areas are too high and cold in winter to be included in milder Zones 15 and 16. In the mildest parts of Zone 7��"in the extreme southern Salinas Valley, for example��"you can get away with growing borderline plants such as citrus, oleanders, and almonds if you choose a spot with good air drainage to take the edge off winter chill. At weather-recording stations in Zone 7, typical winter lows range from 35 to 26°F (2 to ��"3°C),with record lows averaging from 18 to -0° F (��"8 to ��"18°C).

"I'd like the area to be the equivalent of 8a/8b, and also to be able to grow some subtropical things (guava, banana, oranges) but also to be in an area where other fruit trees that prefer cooler climates would grow well too (apples, pears, peaches, apricots, plums, etc.) "

You apparently want Hawaii or Phoenix, but with enough chill days for apples, and you want it in California.

The solution is to buy TWO properties in SoCal, one low altitude near the beach for the subtropicals and one at a higher altitude near Julian for the fruit trees.

We live in Riverside County in Zone 9b (a microclimate). There are varieties of apples and other stone fruit that have low chill requirements. Our Anna apple is the best apple we have ever tasted. It makes wonderful pies, and when friends take a first bite of a fresh apple, "Wow!" That's what they say. You can't buy these at a grocery. They are not a commercial variety. We grow peaches, plums, apricots, persimmon, citrus, guava, mango, Beaumont macadamia, figs, pomegranates, avocados, Pakistan Mulberry and many varieties of wine grapes. We also grow Moringa Oleifera trees with no problems.

Does it freeze here? I've seen it snow, but it doesn't stick. Does it get hot here? Tops 106, but mostly 90-100 degrees.

Good luck in your home search. Try for zone 9b and look for stone fruit with low chill requirements. Subtropicals do well in 9b. True tropicals will struggle. Look for subtropical varieties that can withstand near freezing temps for short times. Zutano Avocado is one.

We are amazed at the climate change at the bottom of our hill to our home. It can vary 5 degrees! Even on our property, one flowering tree of the same variety at the top of the hill will bloom later at the bottom.

Also note California is in a drought, so might not be a good time to plant young trees. They all need water to get established.

Good luck to you!

Sunset zone and different from regular zones. I don't buy into the whole sunset trip, like that book is not at all worth the money. Anything in it can be found better online, it used to be worth it in pre internet days. If you use sunset zones it confuses other people, but I think around San Diego is the area to be able to grow the most tropical stuff and if you are near the water, its not too hot, but it's expensive to buy it that area due to the great climate.

This post was edited by tropical_thought on Sat, Jul 19, 14 at 12:09

Sunset zones are fantastic. Every landscape architect and garden designer I know working in CA uses them. The zone references in the Perry book are invaluable.

You don't have to "buy the whole sunset trip" to understand that Sunset very accurately describes the microclimates in CA. It is only confusing to people who don't live in CA.

This state is comprised of many, many microclimates. The Sunset Western Garden Book sums them all up in one section. Get the book. All you need to do is flip 10 or 15 pages. MUCH easier than searching on the internet, IMHO.

Here in Sunset Zone 15 (Silicon Valley) we can grow citrus, cherries, apricots and wonderful tomatoes...hostas in pots, and well, uh, you know, computers too. ;-)

-Babka

>> I am interested in relocating to California in the future//(with) warm summers and mild winters that has a long growing season.>>

So basically coastal CA. Just bring money. A lot of it. REALLY a lot of it. North, south or central, a six-figure income is just barely middle-class. Home prices in the SF Bay Area are up an average of 18% over last year. For the first time ever, the median sales price in SF has hit $1M.

Real estate is the only economic sector where "trickle-down" actually means something.

Any hillside property will have a considerable difference in microclimates. I'm halfway up (or down) a small hillside, and I have one spot where two expensive Japanese maples, supposedly zone 5-6, have died one after another from frost. 10' away a similar JMaple has quadrupled in size.

But hillside properties are also all about views. Having one means an increase in value from $50-125K over a similar home across the street but with no view.