New Hardiness Zone Map Reflects Warmer Climate

The National Arbor Day Foundation has released a new U.S. Hardiness Zone Map which reflects that many areas have become warmer since 1990 when the last USDA hardiness zone map was published.

In response to requests for up-to-date information to help with tree planting decisions, the Arbor Day Foundation developed the new zones based on the most recent 15 years’ data from the National Oceanic and Atmospheric Administration’s 5,000 National Climatic Data Center cooperative stations across the United States. Hardiness zones are based on average annual low temperatures using 10 degree increments. For example, the average low temperature in zone 3 is -40 to -30 degrees Fahrenheit, while the average low temperature in zone 10 is +30 to +40 degrees Fahrenheit.

Significant portions of many states have shifted at least one full hardiness zone in the new Arbor Day Foundation hardiness map. Much of Illinois, Indiana, and Ohio, for example, have shifted from Zone 5 to a warmer Zone 6. Areas of southern S.D. and southern Minnesota have shifted from Zone 4 to Zone 5. Areas of Minnesota, Montana, and North Dakota climbed from a Zone 3 to Zone 4.

More information can be found online at www.arborday.org.