Lyric discussion by randatronic 

Cover art for It's Thunder and It's Lightning lyrics by We Were Promised Jetpacks

It definitely is "Waiting for my brain to storm" because then he leads to the metaphor of its thunder and its lightning and its all things too frighting referring to his thoughts rather than a literal storm, and follows it with i could hardly see outside as he cant get out of his own mind. at least thats how i interpret it.