WeatherWhys for April 14,2016 from accuweather.com

There are several different types of lightning, but the one to be most concerned about is cloud-to-ground lightning. As soon as thunder is heard, the danger of being struck by lightning is present. Heat lightning is not shown because it does not exist. What people call heat lightning is just distant lightning that can be seen, but no thunder is heard since the sound waves cannot travel as far.