my cat, is an indoor cat, but is petrified of fireworks and especially thunder.
when she hears thunder she hides under the bed cover and shakes..poor thing

although she hates any type of visitor. if she hears a car door....
poof she is gone. she either hides under the bed covers, or under the bed.
but as soon as company leaves and the door shuts she comes out from hiding.

such a silly girl