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[EIRN]

Usually people from STS (most of USA) use USDA Plant Hardiness Zone (ex: 9b, 6a) as climate indicator. It is based only in medium minimum temp. http://planthardiness.ars.usda.gov/PHZMWeb/#
To non USA (and non EU) members this info is no avaliable.
In cientific papers the indicator is Köppen scale. It is based in more climates variables, as temp variation range and medium annual rain fall.
http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification

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[BubbleCat]

So would it seem sensible that we all try to use Köppens system ? I mean its more advanced and precise and yet doesnt require everyone to post vlimate tables

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[Auxin]

I'm sure its useful for some things, but its not more accurate for climates controlling effect on what one can grow in a garden.
In a garden one can regulate water dosage, soil chemistry, sun intensity and direct sunlight time, and to a marginal degree even humidity. What one cant have tremendous control over is winter low temps, which köppen ratings ignore. Look at the map, part of the northernmost region of alaska is the same köppen zone as a large chunk of new mexico! Peyote wont grow above the arctic circle...
Its true that a major limitation of the USDA zone system is its ignoring of overall climate type but that can be remedied easily enough. I typically report my zone as 'semi-arid zone 7a' and, to an experienced gardener, it gives quite a good idea of what can and cant be grown here inside a garden or out in the scrubland.
At the best my 'cheats' for effecting zone effect on a given plant can only move me up or down one full zone ranking unless I bring plants indoors.

USDA zone maps for, effectively, the whole world are available. Recently I've been frequently looking up USDA zone data for mainland china.

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[BubbleCat]

I too thought USDA zones are available for every place except antarktica, but I trusted EIRN and thought I must have been mistaking

I guess the best thing still is to read the key points from a local climate diagram, mean highs, mean lows, max high and min low, summer rainfall winter rainfall sun hours and sun intensity. But thats a lot of info then.

I like your point, the USDA system is aplicable because we can manipulate most factors it doesnt cover and this the mean lows will make the difference. Altho we can not influence the summers highs much either, and sometimes they are the limiting factor.

[Sunshine]

Actually there are USDA plant hardiness zone maps of Europe, among other places. They seem to be a bit more crude. See here ; https://davisla.wordpress.com/plant-zones/

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[BubbleCat]

I have seen highly refined USDA maps of europe before, which doesnt suprise me, there not much to it, read the mean low temperatures for every spot you can get and assign it accordingly. Shpuld there not be a USDA map for some location (which I dont expect) you can also simply look up your mean lowest temperatures and assign yourself your zone, without having to make a map.

So in conclusion the ease of the USDA system lends itself to easy map making, therefore someone probably has covered the whole world in a zone map, probably a computer did the work after being fed the relevant data (temperatures and locations) of weather observatories.