I think one should start where at least my college physical geography class started (ocean and continent influences), then work from there (moisture, temperature, etc). To that I would add in ecoregion and vegetation. Koppen's system used temperature in some classifications (eastern and tropical climes), then ignored temperature in favor of dryness (his steppe or desert), so that's not helpful. Consistency is helpful. Though it's for horticulture and missed contexts by focusing on California, how about Sunset Wester Garden Book's zones? Or one of the ecoregion systems like Bailey or EPA, with some corrections? To me anything tropical needs to require the lowest record temperature be >32F...maybe the 40's to account for truly tropical plants not being damaged. And divided from equatorial, highland, and those above equatorial. Honolulu and maybe Key West make Tropical, but Miami would be in the warm end of Subtropical? Something that works to embrace most latitudes and continents, with probably distinctives of certain continents giving them their own but related zone...like Perth AU vs. San Diego CA vs. Tel Aviv IS. I can give some sample places later if anyone is interested. What do you think? a. Atmospheric moisture, overall tendencies - West Coast Intermountain (deep continental, surrounded by mountains) Continental Dry Continental Humid (like the midwest to the Appalachains) East Coast Upland or Highland Mountain b. Temperature (w/ finer divisions of the below) - Tropical Subtropical Temperate (or mesothermal to microthermal) Boreal Polar / Alpine c. Precipitation (w/ finer divisions of the below) - Wet Moist Semi-arid Arid