I received this article via e-mail. It was a kick in the pants for me, and I hope that it spurs you to do something:
Feeling Warmth, Subtropical Plants Move North
This link will take you to an updated hardiness zones map. It was created by the National Arbor Day Foundation. What will it look like in another 30 years?
Differences between 1990 USDA hardiness zones and 2006 arborday.org hardiness zones reflect warmer climate