The USDA published a new Plant Hardiness Zone map about a week ago. The previous map was produced in 2012 and since that time gardeners have used it to determine what plants are suitable for their yards. The Plant Hardiness Zone map is based on the average lowest temperature a location receives sometime each winter. Zones are produced based on 5 F ranges of that lowest temperature. The new map covers the period 1991-2020, which is also the 30-year period used for the current climate normals.
The new map shows that more than half of the Southeast has shifted its category by half a zone towards a warmer climate. This is not a surprise since the global as well as regional temperature has been rising due to global warming. Practically, it means that gardeners can plant species that can take a little warmer weather and less frost than in previous years. Of course, there can still be outliers like the cold blast that occurred around December 2022, which was much colder than anything else that has occurred in the last 30 years, so if you are conservative you might prefer to use the 2012 map, which is the first map shown below and covers the period from 1976 to 2005.
The 2023 map is available in interactive form at https://planthardiness.ars.usda.gov/. It allows you to search for your location using the zip code or zooming in to your location. The change map below (provided by Chris Daly of PRISM, who produced the original maps) that shows how the zones have changed from the 2012 to the 2023 map are shown below. A half-zone change corresponds to a tan area. The areas in white most likely changed their lowest temperature in the new dataset but not enough to change hardiness zone. There are a few areas that have seen a change in the other direction (towards a colder climate) in the mountainous West, but this is a result of using a bigger dataset than the previous map, which allowed the local climate there to be more correctly categorized.
Also read more at Modern Farmer at USDA’s Updated Plant Hardiness Map Shows Where Growing Zones Are Warming – Modern Farmer.
2012 (old) map:
2023 (new) map:
