Although a Canadian cool front has broken the Midwest's most recent heat wave, medical authorities are still tallying deaths linked to last week's blistering temperatures and assessing why Chicago consistently has a higher rate of fatalities than other big cities in the region and even in the Deep South.

The Cook County Medical Examiner's Office said it had confirmed 11 more heat-related deaths, raising to 80 the number of fatalities here since the heat wave peaked last Thursday after a week of temperatures that climbed to 104 degrees. Medical Examiner Edmund Donoghue said today he expects to confirm a few more deaths -- and even find a few more bodies of live-alone victims -- but that "hopefully the emergency is winding down for us."

In contrast to the record 1995 heat wave that killed more than 700 residents, mostly elderly and poor people who already had serious medical conditions, nearly 100 people have died from the heat in Chicago this summer. Elsewhere, 51 have died in Missouri, most of them in St. Louis; 14 have died in Ohio; and there have been 13 heat-related fatalities in Wisconsin. Southern states such as Georgia, Louisiana and South Carolina, which also sweltered during the nationwide heat wave, have recorded from three to nine deaths each since July 19. Maryland has had two heat-related deaths.

Studies have shown that Chicago, with an average of 2.7 heat deaths per 100,000 people, has a higher rate than Atlanta, Miami and other large southern cities.

Officials here said the simplest explanation is that Chicago has more elderly and poor residents living in older low-income buildings in which air conditioning is not available.

Donoghue said that many hot-weather cities, including Phoenix and Dallas, have up to 99 percent of their houses air-conditioned, while only 75 percent of Chicago's housing units are air-conditioned. He cited figures from the Air Conditioning and Refrigeration Institute, an industry group based in Arlington, showing that 83 percent of new homes nationwide are equipped with air conditioning. Even in the Northeast, 67 percent of new homes are being built with air conditioning, he said.

"The lesson from this is that as the heat belt seems to move northward, we have to stop thinking of air conditioning as a luxury and think of it as a necessity," Donoghue said. "Heat deaths are 100 percent preventable, and we have to get our elderly and ailing residents into a cooler environment."

Housing experts say that even houses in southern cities that do not have air conditioning are often better suited to handle extreme temperatures because of reflective exterior surfaces and better cross-ventilation. In Chicago, many housing units for the elderly and poor are in older brick buildings, which Terry Levin, spokesman for the city's interagency heat emergency task force, said become "heat islands."

City officials said that only four of the 58 Chicago Housing Authority buildings for senior citizens have air conditioning in every unit. Even then, they said, there have been only about a half-dozen heat fatalities in the public housing units for the elderly, largely because of a heat emergency response plan devised after the disastrous 1995 heat wave.

Levin said city workers made visits up to three times a day last week to tens of thousands of elderly residents to check on their condition and urge them to visit "cooling centers" in public buildings.

"We could have had hundreds more deaths if we didn't have the emergency plan," Levin said.

But Levin said a study of each fatality, the victim's living conditions and accessibility to well-being checks by relatives, friends or city workers has found numerous elderly victims who had resisted installing air conditioning either because they could not afford it or because of inflexibility.