TIL that “heat lightning” is a misnomer. It is simply lightning from distant thunderstorms. Lightning can be seen up to 100 miles away in the right conditions, while the sound of thunder doesn’t travel nearly as far.

https://en.wikipedia.org/wiki/Heat_lightning

https://www.reddit.com/r/todayilearned/comments/15plwa3/til_that_heat_lightning_is_a_misnomer_it_is/