The National Weather Service said the record-breaking heat that has baked the nation's midsection for several days was slowly moving into the mid-Atlantic states and Northeast. Excessive-heat warnings remained in place Friday for all of Iowa, Indiana and Illinois as well as much of Wisconsin, Michigan, Missouri, Ohio and Kentucky.
St. Louis hit a record high of 105 on Thursday and a record low of 83 the second day in a row the city has broken records for both temperatures. Temperatures didn't fall below 82 in Chicago, 78 in Milwaukee and 77 in Indianapolis.
"When a day starts out that warm, it doesn't take as much time to reach high temperatures in the low 100s," said Marcia Cronce, a meteorologist with the National Weather Service. "You know it'll be a warm day when you start out at 80 degrees."
In Chicago on Thursday, the Shedd Aquarium lost power as temperatures soared to 103 degrees, a record for July 5. Officials said emergency generators immediately kicked in and the outage never threatened any of animals, but several hundred visitors were sent back out into the heat.
Not even the setting of the sun brought respite as temperatures hovered around 90 degrees downtown at 10 p.m. Some visitors made their way to Millennium Park to splash in the park's kid-friendly Crown Fountain.
"It's hotter here than it is in Arizona," said Mary Dominis, of Tempe, who brought her daughter along to play in the water. "I came here to visit my family and to get away from the heat of Arizona."
Ruben Davila, 32, of Northern California, was also in Chicago visiting family, and at the park seeking some cool relief.
"The heat has made it difficult to walk around and view the sites," said Davila, who was accompanied by his wife and three children.
The heat has been much worse than a mere inconvenience for some. St. Louis officials have reported three heat-related deaths in recent days, and officials in the Chicago area said two people there may have died due to heat Wednesday. A coroner in Rock County, Wis., said the death of an 83-year-old woman there was definitely due to the heat. In Tennessee, authorities have opened a criminal investigation into last week's heat deaths of two young brothers.
It was hot enough to buckle roadways. The Wisconsin State Patrol said the pavement buckled Thursday on Interstate 90 westbound near Madison and on Interstate 39 northbound near Portage, among other places.
With the National Weather Service's heat warning for the city lasting until Saturday afternoon, Chicago Public Schools CEO Jean-Claude Brizard canceled all summer school classes Friday.
Meanwhile, many cities have tried to help by opening cooling centers and extending the hours for their public pools. In some areas, recent storms have knocked out electricity; about 137,000 people in Michigan were without power Friday as temperatures moved steadily toward the 100-degree mark.
Lack of electricity also is likely to compound the misery for many in the storm-ravaged East as the dangerous temperatures move in.
The heat has also taken a toll on agriculture.
Dean Hines, the owner of Hines Ranch Inc. in the western Wisconsin town of Ellsworth, said he found one of his 80 dairy cows dead Thursday, an apparent victim of the heat. He said he was worried about the rest of his herd, in terms of death toll, reproductive consequences and milk production.
"We're using fans and misters to keep them cool," he said. "It's been terrible. When it doesn't cool down at night, the poor animals don't have a chance to cool down."
Associated Press writers Herb McCann in Chicago, David Runk in Michigan and Norman Gomlak in Atlanta contributed to this report.
Hot? Stay-cool tips from desert-savvy Phoenix
People in Phoenix have learned a thing or two about surviving scorching summer days. For those in other parts of the country who aren't used to hearing the weather man say, "It'll be cooling down to 105 tomorrow," here are a few unique tips from the Valley of the Sun:
Keep your ride cool • Those cumbersome windshield reflectors are your new best friend. And if you have young children, buy an extra one to strap over a car seat to keep metal clasps from heating up in the sun as your car sits in the parking lot. You might even throw an ice pack or frozen water bottle in the seat to keep it cool for little ones while you shop.
Get creative about sleeping arrangements • Set up beds on a porch or backyard. Or just sleep in the shade, during the heat of the day.
Avoid the sun • Sure, sunscreen helps. But you can avoid it altogether by waking up and doing yard work before sunrise or going for your daily run at midnight.
Think before you touch • Any surface that sits in the sun could be hot enough to burn. There's no shame in using pot holders to open doors. Also, carry a towel to put on hot seats, and keep curtains pulled tight to block out the rays.
Water is your friend • Drink it. Swim in it. Spray it on your face. In Phoenix, shopping centers and cafes greet visitors by showering them with a fine, cool mist. You can get the same effect by filling a spray bottle with water.
And if all this talk about smoldering temperatures is getting you down, look on the bright side. You can always bake cookies on the dashboard of your car. We really do that.