On the handy map, the USDA switched most of the Austin area from one half-zone, 8B, to another, 9A, which relates to the average annual extreme minimum temperatures. That might seem hard to ...

Thirty years later in 1990, the USDA released an updated Plant Hardiness Zone Map. This map took data from close to 8,000 weather stations and used data from the period from 1974 to 1986.

USDA Plant Hardiness Zone Map (Courtesy: USDA) KXAN Meteorologist Nick Bannin spoke with the USDA about the changes to the zones in the map and what that means for planters here in Central Texas.

The map is based on 30-year averages of the coldest winter temperatures at specific locations, and divides the continental U.S. and Canada into 10 zones, which are further divided into half-zones ...