BY Karin Matz
CHICAGO A stifling heat wave in the nation's midsection intensified on Monday, closing government buildings that lacked air-conditioning and prompting warnings to residents to keep as cool as possible.
The National Weather Service put 18 states stretching from North Dakota to Texas and East to Ohio under a heat warning, watch or advisory. It said as many 13 deaths in the past week in the Midwest could be blamed on the effects of the heat.
When humidity was factored in, the heat index made it feel as hot as 110 degrees in a broad swath of the nation.
"This is unusual," said Pat Slattery, spokesman for the Weather Service. "There's no sugar-coating anything here."
In steamy Oklahoma City, Oklahoma, 13 state government buildings at the capitol were closed after a break in a water main that shut off air-conditioning systems.
Computer systems in Oklahoma's state agencies were turned off and 1,000 employees sent home, said spokeswoman Sara Cowden of the Department of Central Services.
"We're shutting everything down that generates heat," she said.
The extreme drought afflicting the U.S. Southwest has in recent weeks caused water main breaks to quadruple in Oklahoma City to up to 20 a day, said city utility spokeswoman Debbie Ragan.
Des Moines, Iowa, was experiencing its most prolonged heat wave in 20 years, according to Jim Keeney, a meteorologist with the Weather Service.
The hot weather in the nation's breadbasket also posed a threat to farmers' top cash crop, corn, as it enters its key growth stage of pollination. The wet spring led to late planting of corn, and dry hot weather was adding concerns.
"Right now we are seeing real stress in the corn plants," said Mark White, adviser to the Missouri Corn Growers Association.
Persistent high temperatures were particularly dangerous to residents not accustomed to the combination of heat and humidity, Keeney said. Air-conditioning may be the rule in southern states, but many homes in the northern Plains and Midwest do not have it.
Overnight temperatures were not expected to dip low enough to offer a reprieve.
"When you have high humidity, the body's ability to cool down is limited," Keeney said.
CITIES APPLYING LESSONS
The heat was building in Chicago, where temperatures were expected to peak later this week, meteorologist Richard Castro of the Weather Service said.
The city learned a lesson during a blistering 1995 heat wave that was blamed for the deaths of as many as 800 people, many elderly who were in homes without air conditioning.
"That was a really rare event," Castro said. "We're definitely going to see heat and humidity, but that was an unprecedented event."
The city took precautions such as opening cooling centers and issuing warnings to keep hydrated and urging residents not to overdo it during the heat of the day.
The local electric utility, Com Ed, said they had activated an emergency command center to deal with any power issues, but that energy usage was not out of the ordinary.
Other cities echoed those warnings and braced for what could be a week or more of high temperatures.
Excessive heat was forecast to bake the United States from the heartland to the Carolinas -- excluding parts of the Northeast and southern Florida -- through July 29.
In Minneapolis, the Minnesota Twins and the Cleveland Indians had a day-night doubleheader scheduled to begin with the heat index crawling higher.
Ironically, the teams were making up a April contest that was postponed because of extreme cold and rain.
"How about that? The afternoon game here in 100-plus heat index is the makeup game to a game that we had to rain out in 45-degree spitting rain," said Twins' spokesman Kevin Smith.
"Only in Minnesota can we go to those extremes, but that is the name of the game here," he said.
The club stationed water coolers all around the stadium, and relaxed a rule prohibiting fans from bringing in their own water bottles.
In Texas, where a drought has withered crops and sparked wildfires, wildlife rescuers noted that adult deer were abandoning their fawns for lack of grass to eat.
"Nature can be cruel," said animal rescuer Karen Maxfield.
(Reporting by Karin Matz, David Bailey, Steve Olafson, Jim Forsyth, Karen Pierog, Ros Krasny, Kevin Murphy and Suzi Parker; editing by Andrew Stern and Jerry Norton)