City officials said Tuesday they're doing all they can to prepare Indianapolis for several days of high heat and humidity as Indiana swelters under the first of what is expected to be several days of excessive heat warnings.Indianapolis implemented its Extreme Temperature Contingency Plan on Tuesday, which allows the Marion County Health Department to ask community centers to extend hours to provide cooling locations for residents in need. Slideshow: Much Of U.S. Bakes Under Extreme Heat List: Indianapolis Cooling Centers The plan also mobilizes community agencies to aid people who need access to cooled buildings or have other health-related needs."I encourage everyone to check in with elderly neighbors and loved ones who may be susceptible to the extreme conditions," said Mayor Greg Ballard.A call center was activated for residents to access nonemergency heat-related information and to provide cooling site referrals. The number is 317-221-2415, and it will operate from 7 a.m. to 7 p.m. Monday through Friday.Heat indices could exceed 110 degrees later this week, creating a dire situation for people who live in homes without air conditioning and for people who have to work outside.Once the heat index reaches 105 degrees, many people began feeling extreme discomfort, health officials said. Elderly people, newborns, chronically ill and overweight people are most susceptible to heat-related illness. People who have heart or breathing problems are also at higher risk.Dizziness, nausea, vomiting, rapid heartbeat, headaches and changes in mental health are several symptoms of heat-related illness."Heat illnesses can be life-threatening," said Dr. Virginia Caine, director of the Marion County Health Department. "If a person appears to be in trouble, immediate emergency medical care should be obtained by calling 911."Officials recommended that people avoid going outside during the heat of the day if they don't have to be out.