CHICAGO — The upcoming heat wave in the next few days is forcing Chicagoans to reflect on the city’s worst natural disaster in city history — the 1995 heat wave that killed 739.

Temperatures in July 1995 hit 106 degrees, but it felt like 125. Those succumbing to the heat were mostly the elderly in some of the city’s poorest neighborhoods.

Temperatures in the coming days are expected to come close to those in 1995, but they will fall short. The heat wave that year happened over a five-day period, and in the beginning, no one knew what it could look like when it was over.

The extreme heat prompted jokes and fun at City Hall until the numbers came in and proved heat had a cumulative effect — especially on the elderly.

Dr. Edmund Donoghue was the Chief Cook County Medical Examiner in 1995. He and others knew the weather forecast was looking hot, but no one knew what it was going to look like.

“I got a call from the office saying, ‘Dr. Donohgue, we got 40 cases for tomorrow,’ and that was close to an all-time high for the medical examiner’s office,” Donoghue said. “When I got into the office that morning, it was 100 cases. It turned out to be a larger disaster than even I envisioned.”

The death toll eventually reached 739, mostly the elderly, the poor and the isolated.

Donoghue said that on an average day, the medical examiner’s office only handled about 17 cases. During the heat, they dealt with over 100 a day. At one point, they ran into a storage problem.

The city used refrigerated trucks from the Taste of Chicago that summer to help handle the bodies that would turn up at the morgue.

WGN Chief Meteorologist Tom Skilling remembers the 1995 heat wave all too well. He said it was the city’s worst natural disaster in terms of deaths in the city’s history.

The extreme atmospheric elements created the perfect storm.

“To get as hot as we did in July 1995, you had to shut down thunderstorms and cut off lake breeze and we did both. It was no means the atmosphere had to cool itself and the result was the lid came off the temperature. We had the hottest temp ever reported — 106 at Midway and the highest dew point of 83 degrees,” Skilling said. “When you put humidity in the air you shut down the body’s ability to cool itself.”

The biggest lessons learned that summer was heat has a cumulative effect. When you have three consecutive nights where the temperatures don’t drop below 80, coupled with a daytime indices of 110 to 125 degrees, the combination is deadly.

“There weren’t any ambulances available, hospitals in Chicago went on bypass, funeral homes had difficulty picking up the bodies, and later on you couldn’t get an organist for a funeral,” Donoghue said.

Donoghue said one of his biggest jobs was convincing City Hall and the media that this natural disaster was happening.

About 85% of the people in Chicago reportedly had air conditioning back then.It was the other 15% who were suffering in the deadly heat.