The National Weather Service has forecast a high of 109 degrees Saturday in St. Louis, Mo., CNN reported, while Accuweather said temperatures in Philadelphia, Baltimore and Washington, D.C., were expected to rise into the low 100s.
In Chicago, temperatures could climb past 100, which would mark the first time ever of four straight days of temperatures recorded over 100, the Chicago Tribune reported.
Five deaths -- of men ages 48, 58 and 59 and two women ages 81 and 91 -- were attributed to "heat stress," city public health spokesman Efrat Stein said Friday, while another heat-related death was reported elsewhere in Cook County.
Taking into account the intense sun and high humidity, temperatures will feel like they're as high as 115 in some major metropolitan areas, Accuweather said.
CNN said about 350,000 customers in 12 states and in Washington, D.C., still were without power Friday night, and many have not had power for a week after strong storms knocked out electricity.
In West Virginia, about 167,000 customers had no power Friday night.
Lower temperatures were expected with a cold front moving across the Upper Midwest and Great Lakes on Saturday and into Ohio and the northeast Sunday, the National Weather Service said.