I've been thinking of how a new "zone" paradigm would work. If I'm remembering correctly, the current zone system is based off of freezing temperatures. I live in an area that will dip into the mid 20's a few times during the winter, with the last freeze happening in early May (sometimes). We usually have plenty of rain in the winter, but summers are arid, and easily stay above 90F. In addition, there are severe elevation differences, so all that data changes for my neighbors that live higher up. So, I tell people "I'm in zones 6-9." 😜