Plant hardiness zone designations represent the average annual extreme minimum temperatures at a given location during a particular time period. Low temperature during the winter is a huge factor in the survival of plants in different areas!
This helps determine what we can and cannot grow, and about all gardeners/farmers/ anyone in the garden uses this.
The new version of the map includes 13 zones, with the addition for the first time of zones 12 (50 to 60 degrees F) and 13 (60 to 70 degrees F). Each zone is a 10-degree-F band, further divided into A and B 5-degree-F zones.
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.
Compared to the 1990 version, zone boundaries in this edition of the map have shifted in many areas. The new map is generally one 5-degree F half-zone warmer than the previous map throughout much of the United States. This is mostly a result of using temperature data from a longer and more recent time period. The new map uses data measured at weather stations during the 30-year period of 1976 to 2005. In contrast, the 1990 map was based on temperature data from only a 13-year period of 1974 to 1986.
Some of the changes in the zones, however, are a result of new, more sophisticated methods for mapping zones between weather stations. These include algorithms that considered for the first time such factors as changes in elevation, nearness to large bodies of water and position on the terrain, such as valley bottoms and ridge tops. Also, the new map used temperature data from many more stations than the 1990 map. These advances greatly improved the accuracy and detail of the map, especially in mountainous regions of the western United States. In some cases, advances resulted in changes to the cooler zones.
Below is the updated hardiness map for FL..
For anyone else here is a link the new map!!