Why storms are frightening
A storm is more than noise. Dogs may feel changes in air pressure, notice the smell of rain, hear thunder from far away, and sense static electricity. Lightning flashes, wind and rain on the roof add to it. Some researchers think static buildup plays a role, but the evidence is not strong, so treat it as a theory, not a fact.
Fear grows with each storm. The dog learns that the signs predict a bad event, so the fear starts earlier and gets stronger. Without help, it often worsens with age. Sensitivity to sounds and storms can also be linked to other anxieties. See noise sensitivity in dogs.
Fear often looks like: pacing, panting, drooling, hiding, trembling, destroying doors or windows, trying to dig out, clinging to you, and refusing food. Some dogs freeze. Read about fight, flight, freeze, fawn for how these responses fit together.