The summer of 2016 recorded hotter nights than any summer since records began in 1895, according to data released Thursday by the National Oceanic and Atmospheric Administration. The national average low temperature rested at a balmy 60.8 degrees, about 2.4 degrees above average. The reason for the nighttime swelter, especially in the East, was unusually high levels of humidity due to a persistent flow of moisture-laden air off the Gulf of Mexico and Atlantic Ocean, said climate scientist Jake Crouch of NOAA. Summer 2016 tied with 2006 for the fifth-hottest summer on record in the U.S. Only the summers of 1936, 2012, 2011 and 1934 were hotter, NOAA said.