Those precautions include early warnings, well-being checks and more emergency crews on the streets.
In 1995, more than 700 people died during a heat wave Chicago emergency room Doctor David Howes remembers well. He came on duty during the third day and stayed on duty until the heat broke, several days later.
"The overall numbers were overwhelming," Dr. Howes said.
The majority of heat wave victims were elderly citizens living in Chicago's poorest neighborhoods. New York University sociologist Eric Klinenberg wrote a whole book on it. He says many victims didn't have enough money to pay for air conditioning or were too afraid to open windows because of crime. He said many victims lived in brick buildings, which become ovens during extended periods of excessive heat.
"What surprised me the most in my research was the people most at risk of dying in the heat wave were elderly men [who] don't stay in touch with friends, effectively," Klinenberg said.
In 1995, the city didn't reach out to the elderly, Klinenberg said. In his book, he said several department heads were on vacation, leaving the "B Team" in charge.
"Everyone knows that extreme dangers coming, but the fact is people didn't take it as a serious health hazard. They didn't come back to do their jobs," Klinenberg said.
An emergency plan was in place in 1995, but was never activated, Klinenberg said.