A few clouds begin to gather overhead on what otherwise is a sunny day. You wonder somewhat dreamily whether that thunderstorm Channel 6 had been predicting will actually arrive. Your dog already knows the answer, and he's getting frantic about it.

Dogs seem to have a sixth sense when it comes to predicting storms. Long before the skies darken and the rain falls, thunderstorm phobic dogs become agitated, fearful, and clingy. Before we know that a storm is on its way, our dogs may have felt it, heard it, or even smelled it.

How can they do this? And why aren't they doing the weather on the news?

Canines are more sensitive to drops in barometric pressure than humans. Barometric pressure is the pressure of the atmosphere. A drop in pressure means that conditions may be ripe for a storm to develop. A dog may learn to associate this pressure drop with the arrival of a storm. Changes in the static electric field may trigger the same anticipation. Dogs may also pick up the subtle vibrations that precede a storm. A small rumble may be almost imperceptible to us, but not to a dog.

It is also possible for a dog to hear a storm. Dogs can hear at much higher and lower frequencies than we do. A dog can hear a low rumble that a person would miss. Another possibility is that dogs may smell storms coming. Dogs' noses are so sensitive that they can detect concentrations of chemicals in the low parts-per-million range. In fact, dogs' noses are said to be more sensitive than a mass spectrometer. Lightning ionizes air with the formation of ozone – which has a characteristic metallic smell. Perhaps dogs detect this odor, or some other odor associated with the storm.

Finally, a dog may learn to interpret darkened skies and cloud patterns with a storm. You may only learn of the storms imminent arrival through observation of your dog's behavior. For some dogs, thunderstorms are cataclysmic events. They are so frightened by the storm that they may bark, hide, urinate, or defecate, and some dogs become destructive, particularly when forced to endure a storm alone. Others may react to the sound, but may remain relatively calm. The more anxious the dog in thunderstorms, the more he may react before the storm actually arrives.