What is a Heat Zone Map?

Hardiness Zone Maps for gardening show the cold ranges in the United States to help folks make planting decisions. Heat Zone Maps are relatively new. Dividing the United States into 12 regions, this type of map indicates how many days of the year temperatures go above 86 degrees F. This is the temperature at which most garden plants start to suffer. The zones range from Zone 1, with less than one “heat day” per year, to Zone 12, with more than 210 “heat days” per year. Heat Zone Maps will start appearing on seed packets, in catalogs, and elsewhere this fall.