This thunder hour dataset is based on lightning observations from the Lightning Imaging Sensor (LIS) that operated aboard the Tropical Rainfall Measuring Mission satellite from 1 January 1998 to 8 April 2015. The data are provided at 0.05° latitude/longitude resolution for latitudes between 37.725ºS and 37.725ºN. A thunder hour is defined as an hour during which thunder can be heard from a given location. Thunder hours represent a historical measure of lightning occurrence and a metric of thunderstorm frequency that is comparatively less sensitive to geographic variations in the detection capabilities of a lightning location system. Thunder hours are the number of hours in a given year during which two or more LIS group centroids were observed within 15 km of each grid point. The TRMM LIS annual thunder hour dataset is available as a single netCDF-4 file.