USDA Unveils New Climate Zone Map

The U.S. Department of Agriculture (USDA) today released the new version of its Plant Hardiness Zone Map. This is the first update since 1990. This map was jointly developed by USDA's Agricultural Research Service and Oregon State University. It is available online at www.planthardiness.ars.usda.gov.

The map is specifically designed to be internet friendly and interactive. You can click on your state and it will show a close-up with counties clearly delineated.

This new version of the map includes 13 climate zones, 2 more than the previous version. Each zone is a 10-degree Fahrenheit band, and each 10-degree band is further divided into A and B zones, differing by 5-degrees Fahrenheit.

To help develop the new map, USDA and OSU requested that horticultural and climatic experts review the zones in their geographic area, and trial versions of the new map were revised, based on their expert input.

The new climate zone designations are a result of using temperature data from a 30-year period, 1976-2005. The older 1990 map was based only on data from the 13-year period from 1974 to 1986.

More sophisticated data measurement methods factors such as changes in elevation, proximity to bodies of water, and terrain. In addition, the data was collected from more stations than before, resulting in greater accuracy and detail.

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