According to the National Weather Service, the massive heat wave that scorched half of the United States in triple digit heat indexes last week may have been the leading cause of death in as many as 64 cases nationwide.

Though the heat has subsided over much of the coastal States, a return to above average temperatures is predicted for next week.

"The high pressure system responsible for the recent heat wave will remain in place across the central U.S. through Thursday, then a brief reprieve is in store," a National Weather Service statement said.

On Wednesday, portions of the Central U.S. including Kansas, Missouri, Oklahoma, and Illinois remain under excessive heat warnings.  Most of last week's fatalities came from this region.

It's not just humans that are suffering.  The heat has taken its toll on livestock, particularly in the plains states.  A poll of Iowa Cattlemen's Association members indicated that as many as 4,000 head of cattle died from the record-setting heat.

Cattle are particularly vulnerable because they do not sweat and rely only on respiration.

"I've talked to producers who've been out there just constantly looking for things to do to protect those cattle," Dal Grooms of the Iowa Cattlemen's Association told the Des Moines Register. "When it gets to be hot and humid like this, it is just very difficult to stop all losses."

Iowa is the nation's fifth largest cattle feeding state, with a herd of about 3.8 million animals.  The state was hit by heat indexes of as much as 110 degrees last Monday through Wednesday. The heat broke on Thursday and the state received ample rainfall during the weekend.