Las Pilitas has tons of info as you described. You can look up plants by city or zip-link provided below.
Each plant can then be linked to for more info.
I don't know if they have the detailed climate and weather info.

I suppose it would be nice to have all in one website but I don't mind checking the specialty or expert websites based on the info I am looking for.

Here is a link that might be useful: Las Pilitas by zip

thanks gobluedjm.

Heres something I thought about as well.
What would you think of a USDA map with 4 sub zones instead of 2?
The Key-

(Zone 1): below -50f ( same)
(Zone 2) 2a -50f to-48f, 2b -47f to 45f, 2c -44f to -43f, 2d -4sf to -40f.

(Zone 3) 3a -40f to -38f, 3b -37f to -35f, 3c -34f to -33f, 3d -32f to -30
(Zone 4): 4a -30f to -28f, 4b -27f to -25f, 4c -24f to -23f, 4d -22f to -20f
(Zone 5): 5a -20 to -18f, 5b -17f to -15f, 5c -14f to -13f, 5d -12f to -10f.
(Zone 6): 6a -10f to -8f, 6b -7f to -5f,6c -4f to -3f, 6d -2f to 0f.
(Zone 7): 7a 0f- 3f, 7b 4f-5f, 7c 6f-8f, 7d 9f-10f. (Zone 8): 8a 10f-13f, 8b 14f-15f, 8c 16f-18f, 8c 19f-20f.
(Zone 9): 9a 20f-23f, 9b 24f-25f, 9c 26f-28f, 9d 29f-30f
(Zone 10)10a 30f-33f, 10b 34f-35f, 10c 36f-38f, 10d 39f-40f
(zone 11) 40+

Thats getting really specific. I think there will always be micro-climates just because of slight topography changes etc.
Example:
My Lantana freezes and turns black in the back. In front it doesn't. I guess to do more cement and closer to house. I have seen houses nearby theirs doesn't freeze due to asphalt nearby.
So technically are they really a different zone because the asphalt keeps their plants warmer...

I think it has been years since the zones were set and perhaps they do need to be revised.

I think you are over estimating/thinking the value of more precise climatic zones. A difference of two degrees within each USDA climatic zone would serve no useful purpose that I can see, and in fact, relying on lowest cold as the deciding factor in plant suitability is illusory in the first place. There is a lot more to plant suitability than knowing the lowest cold temperature it can tolerate, and this will vary depending on what the summer was like, how hydrated or not the plant was going into the cold, how long the cold lasted and whether it warmed up during the day again or not, etc. Adaptability of plants to a given local will never be an exact science, and is much more dependent on changing weather each year and other factors which combine to affect hardiness.

I think you will gain far more advantage in researching what does grow well in your neighborhood by observing over the years the plants that are long term survivors and may be used as indicator plants for what is hardy/adapted to your area. One must also consider that standards for what hardiness implies will vary by person; you may consider something that survives to regrow but never reaches its full potential as being hardy, while I might not, and prefer my definition of hardiness to assume that said plant will look good or perform to a certain standard based on how I know it grows in a more ideal climate. Ultimately plant suitability is a subjective definition, and your views on plant hardiness may not be the same as someone else's views.

My take is that researching the climate variability, rainfall patterns and temperature fluctuations of the plant's habitat will give a better idea of what it might tolerate, than dissecting the minutia of your local climate. Large mature plants in quantity in a neighborhood are a better indication of general climate and ranges than a 100 charts and tables. As zone designations do not qualify as a guarantee that a particular winter will not drop one or even two zones on the rare occasion, dividing a zone into 4 subcategories seems a complete waste of time to me, and does not substitute for garden experience and thoughtful observation, and intuition/educated surmise about peculiarities of your microclimate that might allow you to be more experimental, or less so.

As an example, I have come to the realization that plants that prefer hot summers to perform well, or to survive a cool wet winter prefer an early warm spring with sustained warmth, are not going to be good choices in my Sunset zone 17 garden. Breaking my climate zone into a 17a/b/c/d designation isn't going to make a bit of difference in growing plants that may grow here, but won't bloom or just don't do very well. I could also say that I already know that a frost tender plant in my garden is going to be much more reliably frost hardy if I grow it under cover of a dense evergreen tree, or up against a house overhang.

I think you also presume that all plants you could potentially buy and plant in your own garden have a horticultural track record sufficient to be knowledgeable about what the range of conditions are that a particular plant will accept. New plant introductions from within the country and outside the country, new inter species hybrids, etc etc all are the sorts of examples that require time, observation and experience in growing to better determine what the limits are.

Zone designations and climatic maps and tables are simply a starting point, one tool among many, and less useful in my opinion that keen observation of what grows well in your area, and where a plant comes from and what the general climate is like where the plant is native. I research a particular garden's hardiness zone/climate by cruising around the neighborhood, looking for indicator plants that from experience I have come to use as reliable predictors of what survives/thrives. If I see these indicator plants doing well in a variety of exposures within a neighborhood, it helps support my conclusions. I also ask older neighbors what has/hasn't worked for them in the past, and prefer to get a 20 year perspective if possible.

Lastly, when a plant is native to a broad range of climatic zones in habitat, this either indicates that said plant is more broadly tolerant of a range of climates, or that there are differences in hardiness across the range of the species, and you won't necessarily know the provenance of said plant at the nursery to know which is which. There is a lot of emphasis on new plant introductions of less hardy plants to search out seed/propagules of these plants from the extremes of their range, so that presumed increased hardiness can be explored. The only way to test this presumed increased hardiness is to trial grow the said plant over several years and a range of temperatures. At one time in the 1940's and 1950's there was an effort to test plants within controlled climatic conditions of something called a Climatron, but this has fallen out of favor, because it can't begin to simulate all the various factors beyond simple range of temperatures that affect hardiness.

Heres why dividing it into 4 might be hepful, some plants may only take 28f, which by the current USDA map thats a z9b ( 25-30f) What if someone thought that because they were in z9b they could grow it, but later find out it dies because there average coldest temp is 26f. By dividing each zone into 4 parts is to help reasure them its a better choice. I know there are alot of other facters that could affect it but lets say everything is the same except the winter lows....

I wasn't suggesting a revised USDA map ( it was an idea that I thought may help), but I was suggesting a new planting guide that would be more helpful.Using the USDA, heat zone map, and SunSet zones together would be a better choice than just one. As as both of us suggested, something that lists what has or is growing in an area is an even better indication. Alot of the things you said above I agree, thats where a new map & guide could come in handy.

Now I wasn't thinking of making this guide, just wondering if you guys think we need a better one, and what should be in it, whats wrong with the current ones, etc. I do think the existing ones are not helpful enough.

And thanks for your replys.

I've got some plants that are supposedly hardy to 32F interplanted with others supposedly hardy to 25F. The last frost turned the 25F's into black goo, while the 32Fs were fine.

I've put out identical thermometers here and there with +/- 0.1F accuracy, and it can be 5 degrees warmer or cooler within the same 10' radius in my garden.

A strong, well fed, correctly watered mature plant can handle a lot more stress than a newly planted one.

Estimates of plant hardiness can vary widely.

Just saying, IMO, there's just so much chance of variation, being more exact is likely of little value. You could put out a lot of identical, accurate thermometers around your garden to determine which spots are the coolest, which are warmest, and planting accordingly. That might be more useful.

I would still suggest that you aren't getting the big picture with the vagaries of climate zones. It makes no difference what your zone normally is when you get a 20 year or 100 year freeze one time that can skew all the average temperature ranges for your zone. While it is helpful to have a general idea of what is suitable for your area, observing what has survived past 20 year freezes is a better indication of hardiness than any zone chart. Knowing what tricks to utilize to maximize your microclimate variations is also more useful to expand your plant choices than some arbitrary subzone designation which isn't consistent from week to week or year to year in any case. Climates are not precise, never will be, and neither are plant hardiness characteristics consistent from year to year. A hot summer versus a cool summer, a dry or wet year will all affect plant hardiness in winter in ways that winter temperatures alone can't predict. I'd still say it is safer to judge the merits of a plant for your climate by what it tolerates where it is native, and your chances of success are further improved if you know how it reacts in other climates similar or close to your own, especially those that may be tougher on those plants than your own.

I have to agree with Bahia, here. There is a reasonable level of resolution for these maps. Attempting additional "refinement" would only misinform.

First of all, consider the questionable validity of the averaging methods being used: static climate maps are made by doing statistical averaging over different study periods (usually 12 years long). Algorithms are then used to interpolate data and draw isotherms between reporting stations. So the sample size is quite small, both in terms of the tiny amount of territory the reporting stations cover and the reach of time in the study period. The USDA map of 1990, therefore, looks different than the 1960 map because, in part, the 1974-1986 examination period used for 1990 did not include many major freeze events in the West.
A more accurate way to show an average minimum temperatures map would be as an animation over, say, a 20-year period. That's how climate really is: it's fluid, changing from one year to the next. Think video, not snapshot.

It's common to come across pat declarations of hardiness, i.e., "hardy to 28F," but such statements are laughable. Hardiness is not established by winter only. The nature of the growing season, exposure and soil quality have a lot to do with it. A plant hardy to 22F in Palm Springs where summers are hot and winters are dry, might die at 30F in Eureka where summers are cool and winters are wet.

Finally, a map is only useful if there is a significant body of literature that will dedicate itself to its use. Sunset may have only its own Western Garden Book going for it, but what a book! After 30 years of using the Sunset WGB, I am increasingly impressed with its accuracy under periodic revision AND...its VALIDITY (the editors understand the limitations of attempts to pigeonhole climate). Many envelope pushers of zone envy along the northern third of the West Coast who have often complained that Sunset was "too conservative" are eating crow after Old Man Winter decimated their marginal plants last year. Climate maps SHOULD be conservative.

It's not high on the list of tools I think I need for my garden. I would pay dearly though for a SoCal species- and climate-specific pruning guide.

This is a quick representation of what I was suggesting. Again this does not exist, nor is it very well made. This is just to show you what I meant on my posts...

Something along this line...
{{gwi:558987}}
contains : USDA map, SunSet maps, Heat Zone Maps, links to those websites,& a search function.

after you search a certain plant:

{{gwi:558989}}
this shows once you search a plant, it shows you a pic, places it has been known to grow, how to take care of it, pest and disease and much more. Has a comment box where anyone can chat about it etc. in text it would also teach you about microclimates, marginal places it may or may not be grown. How to protect it in winter, area code reference of climate, records high and low, and more.

all of these I got from a bunch of different websites (except for 1). That is another reason for it to ALL be in one location, not a bunch of different locations.

Well I Agree probably because I just moved here and there are sometimes differences with in one zip code but basically I wish garden forums would have a map where one could post how and what I successfully grew.
When you first get here I do not know what to fall seed northern Nevada I had south facing wall with asphalt in front I grew Marigolds so successfully that I had flowers 14 of November one year we had a late frost that year it was awesome!The trial and error of gardening is sometimes backbreaking work

Yes, too many micro-climates and too much intellectualizing of something that should (if you pay attention to what is going on around you) come naturally to you. I'd rather be out in the garden than sitting at a computer.

I understand the USDA is revising its maps, but I think it's still in draft form, last I heard.

Although I'd like to see Sunset break up its zone 17, truth is I agree with the others. Microclimates, especially in urban areas with small property lots, make a huge difference in the garden.

I think your idea is laudable, but you'd be spending a lot of time on something that can't really be validated without the help of a lot of other people over an extended period of time. Are you sure that's what you want to be doing with your life?

I am in a semi-rural area and most of us have several to fractional acres and we still have micro-climates. As one person said, with there being much difference between the front yard and the back and so on. Even plants sold at the nursery which is less than two miles from where I live will freeze to the ground every 10 or so years when we get down into the teens.

I have to agree with others. This is an indomitable task and would never be more than a "general guide" due to, as others have said, various microclimates in one's own yard and "fluid climate" esp. now with global warming.

If you are driven to take on this project, I applaud you, and it will probably be used, but I just don't see that gardening/hardiness/etc. can ever be an exact science. There are just way too many variables as mentioned, and including the way one gardens in general (i.e. watering, companion plants, etc.)

These forums are one of the best resources, aside from Sunset, because actual people share their methods and experience. JMO

wanda

There are numerous places that do average last frost date as well. And degree days. And chilling hours. And CIMIS has history. No need to reinvent the wheel.

Dan