What is the name of the song released in the 1990's that was techno instrumental and started with the sound of thunder?

The song you're referring to is likely "Children" by Robert Miles, released in 1996. It features a distinctive piano melody and a techno instrumental style, starting with the sound of thunder, which sets an atmospheric tone for the track. "Children" became a significant hit in the 90s and is often associated with the trance music genre.