Help please with 'exterior zones' (A,B,D,E,etc) for outdoor growing

Hey all.
doing my first outside guerilla this year.
I am confused (kinda) on exterior growing zones. I guess they are climate zones that are designated a letter; a,b.c, or whataver.
I cannot seem to find a map of the zones, in order to know what zone im in.
Can someone help out with a map.....I cant be the only one wondering this info.
Seed sellers will say something like;
Suitable for exterior zone A,B,C, (E).
Ive tried googling it but cant find it.
So, ya, some help would be awesome.
Happy Growing......

Theres a decent one on Mandala's seeds website. But it may only be good for their strains.. Heres the link, hope it helps.

http://www.mandalaseeds.com/Guides/Marijuana-Outdoor

im pretty sure thats what im looking for...seems to be anyways. thanks

Not a problem.