The most common type of lightning in a thunderstorm is in-cloud lightning, which occurs within the cloud itself. An extremely rare form of lightning is called ball lightning. It is so rare that scientists often question its existence. Those who have witnessed ball lightning describe it as a round ball of fire seen on telephone wires or entering through windows and doors during a thunderstorm. Then there's heat lightning.
Heat lightning has nothing to do with how warm temperatures are on a summer's night.
It is actually lightning seen from a distant thunderstorm too far away for the thunder to be heard. Follow weather reports. Make sure a battery-powered radio is nearby. Do not turn on the television. Listen to Noaa Weather Radio for the most current information.