As record heat enveloped the nation, the rate of emergency room visits increased compared with the previous five years, a sign of the major health risks of high temperatures.As record heat enveloped the nation, the rate of emergency room visits increased compared with the previous five years, a sign of the major health risks of high temperatures.Read MoreHeat and Heat Waves, Heatstroke, Centers for Disease Control and Prevention, Weather, Global Warming, Research, Southern States (US), United States Politics and GovernmentNYT > Health