Changes in Hardiness Zones

Arbor Day Foundation

This animation illustrates how the hardiness zones for plants have changed between 1990 and 2006 based data from 5,000 National Climatic Data Center cooperative stations across the continental United States.

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Notes from our reviewers

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This would be a good tool to introduce the idea that climate warming affects society in various ways.
Hardiness zones are determined by the coldest wintertime temperature expected in a given location. The actual low temperature could be higher or lower than that specified by the hardiness zone. The Arbor Day Foundation determined a need for a new hardiness zone map and used NOAA data to create the newer 2006 map [http://www.arborday.org/media/zonechanges2006.cfm]. The US Department of Agriculture continues to use the map they generated in 1990. A related map shows where the largest changes from 1990 to 2006 have occurred: [http://www.arborday.org/media/map_change.cfm]. Comments from expert scientist: The changes of the hardiness zones in the U.S. are consistent with the phenolgy changes reported in the scientific literature.
When the user presses "play" there is a visible shift in the hardiness zone from 1990 to 2006. When the user presses "difference," the shifts across zones are highlighted. There is some commentary about these maps in the press release - [http://www.arborday.org/media/zonechanges2006.cfm] A high-resolution version of this map is available for download.