U.S. Hardiness Zone Changes Between 1990 and 2006. The Arbor Day Foundation

Much of the U. S. has been warmer in recent years, and that affects which trees are right for planting. The Arbor Day Foundation has recently completed an extensive updating of U.S. Hardiness Zones based upon data from 5,000 National Climatic Data Center cooperative stations across the continental United States.

Hardiness Zone Changes Between 1990 and 2006 via The Oil Drum