When the label says a certain number of chill hours are needed, what maximum temperature are they talking about?

I recently bought some apple, Asian pear and cherry trees and they all require chill hours. I live in southern California so I know we don't get very many hours of low temps. I also know that big box stores don't typically sell trees that are not suited for the area you are in.

Am I destined to have trees that just produce nice flowers? What are the max temps that these chill hours refer to?

Chill Hours refers to the accumulated hours under 45 degrees.
If your seeing something that says that type need 300 chill hours, then your best to be in a area that will receive 300 or more accumulated hours under 45.

OK, 45 degrees isn't too bad. Cumulative hours might be a problem. Is there any site that lists total chill hours for an area?

http://www.raintreenursery.com/chill_hours.htm Also, be careful when looking at older chill hour and USDA zone maps because of global warming the country has been experiencing alot less chill hours than we did years ago. http://articles.latimes.com/2009/jul/22/local/me-climate-farms22