Temperatures as high as 99 degrees Fahrenheit (37.2 Celsius) were forecast for the Washington area for Sunday

Children play in a fountain in Silver Spring, Maryland, north of Washington, DC, on Saturday as temperatures soar above 100 degrees Fahrenheit (38 degrees Celsius). A scorching heatwave searing the United States was expected to begin to ease slightly Sunday, but authorities warned that temperatures will still remain high and dangerous through most of the weekend.