The recent heat wave was blamed for seven more deaths in the city yesterday, bringing to 15 the number of people to succumb during the four days of 90-plus temperatures.

All but one - a 53-year-old man who died of heatstroke outdoors - were found in overheated houses, some sealed tight.

The toll far surpassed the three heat-related deaths recorded last year. There were seven heat deaths in 2003, two in 2004, 23 in 2005, and 27 in 2006, officials said.

The season's first heat wave began Saturday with a high of 94 degrees, and continued with high temperatures and oppressive humidity before breaking Tuesday night.

Jeff Moran, a spokesman for the Medical Examiner's Office, said the latest fatalities were found Wednesday and were ruled heat-related yesterday. Under a new policy, none of the deceased was identified.

James Dean, medical director for the city Health Department, said the first heat wave of the season usually is the deadliest.

The 15 fatalities ranged in age from 42 to 97. Most had underlying conditions, including cardiovascular disease, diabetes and dementia.

The youngest had emphysema and a history of mental illness, Moran said.

Most also lacked air-conditioning in their homes. In several cases, fans and open windows proved insufficient.

While heat-related deaths are preventable, Dean noted that the city had come a long way from 1993, when high temperatures were blamed in the deaths of 105 people.

After that, the city became a national leader in warning of the health dangers associated with heat, offering advice and opening air-conditioned community centers to those most at risk.

"The body can take several days to acclimate to extreme temperatures," Dean said. "On top of that, the elderly, who are most susceptible, do not acclimate as well."

He said some medications that elderly people take for chronic disease also "can interfere with the body's ability to acclimate."

Many of the victims lived alone, he said, which is why the city advocates a buddy system under which neighbors and relatives check on the elderly.

The 15 fatalities included nine women and six men.

The oldest, a 97-year-old woman, was found on the second floor of a home in North Philadelphia where an air conditioner was operating on the first floor, Moran said.

"It still was very hot," he said.