Thunder rang through the dark sky as rain pelted against the ground like a thousand angry hornets.
I don't think that's a particularly good metaphor. I have trouble visualizing "a thousand angry hornets" striking the ground. Surely you could compare it to something else.
The second sentence needs better punctuation. Either break it up into two sentences, or insert a semi-colon ( ; ) before "however."
I disagree that there's any need to give the girl a name at this point. Develop the details gradually. I also think you're better off writing the story prom the p.o.v. of an omniscient observer rather than the girl. It's tricky choosing the right vocabulary when you're pretending to be a nine-year-old.