Continental US displaying raw NDVI values with average dates of first fall frost overlayed and Canada and Mexico masked out. 
Agricultural Statistics District boundaries are displayed in brown and state boundaries are black. 
Image displayed on graphic is 2012.
See the comparable Weekly Weather and Crop Bulletin at <"http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1393">Weekly Weather and Crop Bulletin</a> for details.