ST. LOUIS – Much of the nation continued to sweat Tuesday under oppressive heat, made worse by high humidity, that stretched from the Midwest to the East Coast.

Temperatures reached well into the 90s and in some cases above 100 degrees, a trend expected to continue through the weekend in parts of the South and Midwest. The National Weather Service issued excessive-heat warnings in several states, and health officials urged people and pets to stay in air conditioning.

Three deaths were blamed on the heat, and the nation’s biggest public utility said its 8.7 million customers set an all-time peak record for power consumption Monday. The Tennessee Valley Authority expected that record of 32,095 megawatts to be broken Tuesday and perhaps again later this week.

“Wednesday will be hotter than today. Thursday will be hotter than Wednesday. And Friday will be hotter than Thursday,” spokesman Gil Francis said. “So it looks like we could have five straight days of record peak power demand.”

In St. Louis, where the heat index – how the air feels because of the combination of heat and humidity – was 101 degrees by early afternoon, more than 80 cooling centers were opened. High school football practices moved indoors or to early mornings. The city extended hours at swimming pools and kept sprinklers at recreation centers running day and night.

The utility company Ameren Corp. and church and civic groups announced fan and air conditioner giveaways to help the needy cope.

In nearby Sparta, Ill., thousands of shooters at the yearly Grand American World Trapshooting Championship pressed on with competition despite the triple-digit heat index. Several competitors were treated by on-site ambulance workers for heat-related troubles.

“It’s awful,” tournament director Mike Hampton said. “We’re using up a lot of Gatorade, lots of water. We have two or three water jugs on all the shooting fields.”

Most of Georgia and Tennessee were under a heat advisory Tuesday, with the Weather Service predicting a high of 99 degrees for the Atlanta area, perhaps even higher in Memphis and Nashville.

High humidity could make it feel like 110 degrees today in Cincinnati. In Dayton, public schools were closed Tuesday, just a day after opening. Many of the district’s buildings lack air conditioning, and classes were also canceled Wednesday.

In Oklahoma, health officials said heat was suspected in death of a 47-year-old who collapsed Thursday working on train tracks in Panama. Jesus Tovas had a body temperature of 107.9 when he was taken to a hospital. Arkansas had recorded two heat-related deaths.

On the East Coast, horse races were canceled Tuesday at Delaware Park the heat was a threat to horses and jockeys, track officials said.