A significant chunk of the Lower 48 is under some sort of heat alert as a significant heatwave is underway. This includes large portions of the Plains, Midwest, Ohio Valley, and Mid-Atlantic. And Michiana falls right in the middle.

The heat and humidity expected to be in place Thursday to Saturday will create dangerous to life-threatening conditions for anyone who has to spend time outdoors. Even the healthiest of people can succumb to heat of this magnitude. 

Maximum heat indices will rise to 103°-110° in Northern Indiana and Southwest Lower Michigan each of the three days. Surrounding states like Illinois, Wisconsin, Iowa, Missouri, Kentucky, and Ohio will see similar, if not hotter, heat indexes.

These kinds of heat indexes, which combine the air temperatures and humidity, can result in heat-related illness. Depending on what you're doing and where you're doing it, heat-related illness could develop in a very short period of time without you knowing it, according to health experts.

Dr. James Devereaux, a physician in Bloomington, Indiana, says heat should not be taken lightly. "Heat is a killer. It is the number one killer when it comes to extreme weather events," he tells ABC 57 News.

And when asked about the impending heatwave, Dr. Devereaux says to not brush it off as if it's nothing.

"It does not matter how well you're conditioned. It does not matter how tough you feel you are. It can affect all individuals."

There are things you can do to protect yourself from heat-related illnesses. Some of them are:

•Minimize time in direct sunlight

•Stay hydrated; avoid beverages with sugar, caffeine and alcohol

•Eat cool, light and easy-to-eat foods like salad and fruit

•Wear loose-fitting and light-colored clothing

•Avoid the outdoors from 10 a.m. to 5 p.m.

•Check on your family, friends, neighbors and pets before, during and after a heatwave