Oppressive heat, humidity and a chance of strong to severe thunderstorms pepper the forecast for Wednesday and Thursday as central and southern Indiana experience the hottest weather in three years.A heat advisory is in effect from noon until 8 p.m. on both Wednesday and Thursday as Indiana bakes in temperatures in the mid- to upper 90s and heat indices between 105 to 110 degrees.Indianapolis on Tuesday implemented its extreme heat plan, extending the hours of the city's pools and spray grounds.Fire hydrants were opened in some areas without pools nearby. Air-conditioned community centers are staying open for extended hours.A list of pools, community centers and spray grounds can be found here . Steamy Weather Prompts Concern For State Fair The Indiana State Fair kicked off Wednesday morning in the midst of the heat.High school bands that hit the ground marching for the Marching Band Contest, which begins Wednesday, are taking precautions to avoid heat-related illnesses.Cardinal Ritter High School held practice on Tuesday night in preparation for fair activities, but that practice was cut short because of extreme heat and humidity."I'm cutting practice today in half. I had planned on going until 9 p.m. We're going 'til 7:30," said band director Edward Guanajuato. "My principal and I both agree, especially my principal. She said it would be best if we didn't march in uniforms tomorrow for the simple reason that it is so hot."Children, along with the elderly, are especially susceptible to heat-related illness. Everyone should take frequent breaks, drink plenty of water and/or sports drinks."This is a time for coaches and school officials to say, 'Let's start introducing these kids to the hot weather environment and, over a period of seven to 10 days, let's start doing some short drills outside and introduce them to the hot weather over time," said Dr. Meena Garg of the Indiana University Center for Sports Medicine.Warning signs of heat-related illness included light-headedness, a fast beating heart, profuse sweating and heat cramps. Strong To Severe Storms Possible The extreme heat and humidity are expected to spark thunderstorms, some of which could be strong or severe on Wednesday and Thursday.The biggest severe weather threat will be in the northern half of the state, closer to a frontal system that divides the steamy air to the south from relatively dry and cool air to the north.Strong winds are the primary threat from the storms, but large hail and a few tornadoes are also possible.The severe weather threat on Wednesday is generally from the Indianapolis area northwestward. On Thursday, all of northern and central Indiana could see strong to severe storms.