Well, you need:

Madonna - Rain
Les Miserables - A Little Fall of Rain
Miri Ben-Ari - Sunshine to the Rain
Don Henley - Come Rain or Come Shine
David Gray - Gutters Full of Rain
Jane Siberry - It Can't Rain All The Time
Jim Brickman - Lake Erie Rainfall
Amanda Marshall - Let It Rain
Guns 'n' Roses - November Rain
Blue Rodeo - Rain Down On Me
Counting Crows - Rain King
Counting Crows - Raining in Baltimore



Bonus:
Amanda Marshall - Inside the Tornado
Live - Lightning Crashes
10,000 Maniacs - Like the Weather
Disney - Little April Shower (Bambi, I think?)
Enya - Storms in Africa
Various - Stormy Weather