Part of the natural evolution of the National Fire Danger Rating System (NFDRS) is a change in spatial resolution of inputs and ratings from point to grid. To achieve this, the live fuel moisture model within NFDRS will need to be automated. Currently, a manual "switch" associated with each NFDRS weather station begins a period of increased live fuel moisture and reduced fire danger ratings. This "switch" is known as the Green-up date for the 1978 version of NFDRS. A method to objectively designate the Green-up date is proposed using a 1-week composite of 1km Normalized Difference Vegetation Index (NDVI) data from the Advanced Very High Resolution Radiometer. Green-up date is based on the area under the curve of a smoother applied to the climatology of each week for the 1km pixel. The area under the climatology curve from NDVImin to NDVI(max-min)*0.5 becomes the target area. With the smoother applied to a given year's NDVI values, green-up begins when the area under the curve from NDVImin to NDVI(max-min)*0.5 achieves the target area. The approach is primarily designed for operational use; however, historical Green-up dates also can be determined back to 1991. Examples of the application of this method are provided for mixed conifer forest, pinyon-juniper woodland, and southern rough in California, Nevada, and Florida respectively.