L.C.
Try getting her some story books about rain and storms that you can read her. Their is one called KISS GOODNIGHT that is really cute.
The story is a simple one. Sam's mother is putting Sam to bed, but when she asks Sam if he is ready, he replies, "Oh, no. I'm waiting." Mrs. Bear quietly and affectionately tries several different activities to prepare Sam for bed. First, she reads him his favorite book; then, with the wind howling outside, she carefully tucks him in. As the rain begins to fall with a "Splat!" on the roof, she arranges all of Sam's stuffed toys around him. Finally, they both drink glasses of warm milk. After each of these activities, Mrs. Bear asks Sam if he is ready for bed, but he continues to reply, "Oh, no. I'm waiting." Mrs. Bear reviews everything they have done and realizes that she has forgotten to kiss Sam good night. After lots of kisses, despite the bad storm outside, Sam goes happily to sleep.
You could also give her showers instead of baths and sing songs like, SINGING IN THE RAIN and let her know that being in the shower is just like being in the rain.
Help her count how long it takes to hear a clap of thunder, after a flash of lighting, to calculate how far away a storm is. This could a teaching moment for her and you can do some math. For example....this time it took 5 seconds to hear thunder after the lighting next time it took 2, how much is 5 + 2. Get her thinking of something other then the rain/storm.
Good luck.