Anxiety in dogs and cats can be triggered by various external stimuli. Dogs and cats often fear loud noises (e.g. fireworks), household visitors, nail trimming, car travel, vacuum cleaners, or separation from their owners. Fear of thunderstorms is a common cause of canine anxiety. Dogs and cats become anxious when they see lightning bolts or hear the constant pounding of rain on the roof. They also detect changes in barometric pressure and the ozone content of the air (a side effect of lightning) that occur during storms. And if they receive a shock from the buildup of static electricity, dogs really become nervous. It’s no wonder why so many dogs suffer from “storm phobia.”