Thundercake by Patricia Polacco (This one's going on our All-Time Favorites list.)
Flash, Crash, Rumble and Roll by Franklyn M. Branley (Let's Read and Find Out Science)
Thunderbolt: Learning About Lightning by Jonathan D. Kahl (good pictures of lightning and storm clouds)
How Ben Franklin Stole the Lightning by Rosalyn Schanzer
The Weather Wiz Kids site has lots of good info. on thunder and lightning, as well as other weather topics.
Just a couple more of these weather posts, and then I'll be done - I promise. And in case you're wondering, we finished with weather weeks ago. Now we're onto gardening...more on that soon. :)