can`t you buy them from a newage shop?My mum had a thunder storm one that she liked to listen to in bed,in fact she listened to it on her death bed and wouldn`t let anyone turn it off!Strange considering that she was terrified of real thunder,bless.
it probably not what ur lookin for but the intro to the origional set u free by n trance has a storm thundering away befor the piano tune comes in...?
and not sure if im right here but doesnt an old enigma tune hav the sound of rain?
Mystic Moods Orchestra practically made a whole career off the back of an album called "One Stormy Night"; it's an easy listening album of orchestral stuff with rain and storms in the background. You'd have to order it from Amazon.com (i.e. the American site), though, because Amazon.co.uk doesn't seem to have it, and I've never seen it in a British store.
Many years ago I think there was a song called "Rythem of the rain" and was sung by a well known group at that time. It started with a crash of thunder and then the sound of pouring rain.
I meant to say it was on 'The Who' film soundtrack album 'Quadrophenia' and is available as a download on AllofMp3 and probably iTunes (their website is down at the moment).