Hardiness zone question
I have been confused on this hardiness zone thing.. I live in an area where I can't tell for sure if I am in zone 7 or 8 because I appear to be near the line. I wish I could find a zone map that had cities and towns overlain on it.
Anyways, what is the most important thing about the zone? Is it the cold temp or the warm temp that is important? For instance, a cherry tree I bought is listed for zones 5-7. Is that the hardiness rating for cold-hardiness or how much heat it can withstand?
Lastly, is there such a internet site or tool that one can use to determine how many chill hours are in your area?
Thanks in advance.