A "roller coaster" heat wave that has killed 187 people locked much of the nation from California to New York in a sauna bath yesterday, with temperatures in some heartland cities climbing back into the 100s.

Some relief from the heat came from thunderstorms spreading across the Midwest into the Great Lakes region and parts of the Eastern Seaboard. But the same storms ripped roofs off buildings in parts of Kansas with 100-mph winds and knocked out power to more than 100,000 homes and businesses in western Michigan and the Detroit area.

Temperatures were in the 90s from California to New York, with some cities in the Southest and mid-Mississippi Valley reporting triple-digits.

In Chicago, meanwhile, the Cook County medical examiner ruled that the deaths of four people in a sweltering West Side nursing home last weekend were homicides in which "heat was a contributing factor."

The bodies of the victims, who had been critically ill, were discovered in their top-floor rooms at the Center for Human Development Nursing Center last Saturday by city health inspectors making an unannounced inspection.

The air-conditioning system was not working at the time, and officials said temperatures in the rooms reached 105.

"We intend to find out who was responsible and prosecute them if it is warranted," a spokesman for the state's attorney's office said.