By Brendan O'Brien
CHICAGO (Reuters) - Another sweltering hot day loomed on Wednesday for the middle third of the United States, where dangerously high temperatures were stuck well above normal while officials warned people to stay indoors and hydrated.
Millions of Americans who live in major cities such as Chicago, Detroit and Atlanta were under heat advisories as the heat index, a measure of what the temperature feels like to the human body, was to climb past 100 degrees Fahrenheit (38 C), the National Weather Service (NWS) said.
"Extreme heat and humidity will significantly increase the potential for heat related illnesses particularly for those working or participating in outdoor activities," it said.
It was to be the second day of stifling weather for the middle third of the nation, from Wisconsin and Michigan south through Tennessee and Georgia and into Florida where temperatures flirted with records in some spots.
Forecasters and local officials warned residents to drink plenty of fluids, stay indoors and check up on relatives and neighbors during the day. Many municipalities have set up cooling stations and centers to help residents get out of the heat.
More than 325,000 homes and businesses in Ohio, West Virginia, Indiana, Michigan and Wisconsin were without electricity on Wednesday morning, Poweroutage.us reported.