The USDA Plant Hardiness Map has been updated and is now available as an interactive GIS-based map. The last update took place in 1990. Many zone boundaries have shifted due to the use of more sophisticated technologies and data collection spanning over a 30-year period. The new version is more accurate and detailed. Check out the New Map!
“Plant hardiness zone designations represent the average annual extreme minimum temperatures at a given location during a particular time period. They do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature for the location over a specified time. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.
The new version of the map includes 13 zones, with the addition for the first time of zones 12 (50-60 degrees F) and 13 (60-70 degrees F). Each zone is a 10-degree Fahrenheit band, further divided into A and B 5-degree Fahrenheit zones.”