Plant Zones – are you confused? Me, too. Who can remember all this stuff?! This should help.
I’m a 10 (in my dreams!) and a 24. More specifically, I live in Zone 10 in USDA Plant Hardiness Zones and Zone 24 in the Sunset Garden Climate Zones. The difference is that the U.S.D.A. maps tell you only where a plant may survive the winter; Sunset climate zones show where that plant will thrive year-round. Sunset also takes other factors into account: latitude, elevation, ocean influence, mountains, hills, and valleys.