The USDA Plant Hardiness Zone Map is the national standard to determine which plants (and palm trees) are most likely to thrive in a specific location.
The map is based on the average annual extreme minimum winter temperature during a 30-year period in the past, divided into 10-degree Fahrenheit zones. Note that these zones are not based on the lowest temperature that has ever occurred in the past or might occur in the future. Please keep that in mind when selecting palm trees, especially if you’re considering growing palms that are not rated for your zone.
In addition, although this edition of the USDA PHZM is drawn in the most detailed scale to date, there might still be microclimates that are too small to show up on the map. Microclimates, which are fine-scale climate variations, can be small heat islands—such as those caused by extremely large amounts of blacktop and concrete—or cool spots caused by hills and valleys.
For a more interactive version of this map, click here to go to the USDA website.