Urban heat penalty (IMAGE) DOE/Pacific Northwest National Laboratory Caption Urban areas are hotter than rural areas—and the heat stress penalty in U.S. cities is particularly strong during nighttime hours. Credit Animation by Sara Levine | Pacific Northwest National Laboratory Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.