Yellowstone Lake (IMAGE) University of Wyoming Caption Yellowstone Lake, North America’s largest high-elevation lake, freezes over completely in late December or early January and usually thaws in late May or early June. The period of ice cover has not changed in the last century, despite warming temperatures in the region. Credit Lusha Tronstad 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.