Residents across the South and Midwest were hopeful that the weekend would bring some relief from brutal temperatures that have killed more than three dozen people and set records for power demand.

Forecasters expected temperatures in Memphis and other parts of the Mississippi Valley on Friday to drop slightly, into the 90s, a relief from several consecutive days of triple digits.

In Tennessee, the Shelby County medical examiner's office confirmed Friday that heat caused the death of a 77-year-old woman found in her home the day before, bringing the death toll in Memphis alone to nine.

In all, 41 deaths in the South and Midwest have been confirmed as heat-related, and other deaths are suspected, authorities said.

The Tennessee Valley Authority, the nation's largest public utility, shut down one of three units at the Browns Ferry nuclear plant in Athens, Ala., on Thursday because water drawn from the Tennessee River was exceeding a 90-degree average over 24 hours.

"We don't believe we've ever shut down a nuclear unit because of river temperature," said John Moulton, spokesman for the Knoxville, Tenn.-based utility.

The shutdown posed no safety threat, but it came as TVA hit records for power consumption in the last two weeks in its service area covering most of Tennessee and parts of Alabama, Mississippi, Kentucky, Georgia, North Carolina and Virginia.

The utility will compensate for the loss of power by buying it elsewhere.

In north-central Arkansas, the temperature reached 112 degrees on Wednesday in a place called Evening Shade.

"It's miserable," said Sharp County Judge Larry Brown, the county's chief administrative officer. Road crews were working shorter hours, "coming in early and leaving at noon. By then it's already way over 100 anyway," Brown said.

At midafternoon Thursday it was 107, Brown said. "It's still like an oven," he said.

Emergency physicians warned that days of heat-related stress can lead to problems such as nausea, dizziness, headaches, cramps and vomiting for people who otherwise are healthy. Those symptoms are the first signs of heat exhaustion.

"It is a cumulative thing," said Dr. Franc Fenaughty, an emergency room physician in the Memphis suburb of Germantown. "After four or five or six days you are going to see more people get dehydrated. And, the big problem is dehydration."

Untreated, heat exhaustion can lead to heat stroke, which often causes death or disability. A fever of 101 degrees or higher, especially for older people, is cause for concern, and fever of 103.5 or more is considered an emergency.

"Every day the risk rises for those people who haven't had a break from the heat," said Dr. Mary Ellen McIntire, of the Baptist Minor Medical Centers.

There were nine confirmed deaths in Missouri, eight confirmed deaths in Illinois, four each in Arkansas and Georgia, three in Alabama, two in South Carolina and one in Mississippi, as well as one death in Tennessee outside Memphis.

Last summer, a heat wave killed at least 50 people in the Midwest and East. California officially reported a death toll of 143, but authorities last month acknowledged the number may have been far higher. A 1995 heat wave in Chicago was blamed for 700 deaths.