In my meetings this week I was reminded that many farmers use USDA planting zones to determine what varieties of trees and crops to plant. Hardiness zones are related to the average coldest day of the year.  Here is an interesting comparison of how these zones have changed over time due to the warming trend we have seen in the US since the 1960s and 1970s. You can view it at https://noaa.maps.arcgis.com/apps/MapSeries/index.html?appid=5f617f338eb5431eb3700e8685eccaf7.