Fear of Thunder?

[Twixter]

It seems that everytime there is a storm outside, as there is right now, the rats are very on edge. The two youngsters, who will both be nine weeks old on Saturday, are quite literally freaking out. I've never had rats who act this way  before. And I believe the actions of the babies are making the older rats nervous. When the thunder is particularly loud, they'll jump and run for cover in their huts.
Following what I know about dogs, I haven't tried to comfort them or payed any attention to them whatsoever. There's really no place in the house I can put them where they wont hear the thunder, and I'm afraid they're going to end up having some sort of panic attack or hurting themselves, as they're running around like crazy.

Does anyone have any advice? I just picked up Italy, and her poor heart feels like it's about to burst out of her chest.