A combination of wind, thunder, lightning, change in barometric pressure, static electricity, & low-frequency rumbles preceding a storm (that we can't hear) all play a role in stressing dogs out.
Unfortunately, there is no easy, one-and-done fix. But there are lots of tools to reduce your dog's distress during a storm.
1. Reward calm behavior YEAR-ROUND. Practice creating calm every day. It’s best to let your dog self-sooth and not coddle them while they are in a panicked state of mind. Remember, you get what you pet.
2. Give the dog a safe place to go in a storm.
Provide access to a quiet, dark space where the dog can't hear or see what's happening outside. LET YOUR DOG DECIDE where they seek sanctuary (open crate, bathroom, basement, under your bed). Allow them to safely move freely around the house. Put on calming music for background noise and diffuse PURE essential oils like lavender.
3. Consider a snug garment.
Some dogs benefit from items like a weighted garment (a Thundershirt), or a metal fabric-lined cape (The Storm Defender), that claims to protect from static shocks. Some folks also rub dryer sheets in their fur to help eliminate static build up, but be cautious as those chemicals can be irritating to dogs.
4. Work on desensitizing your dog YEAR-ROUND to the sounds of a storm.
Play YouTube clips of thunder at low levels while you train, work, play with them. Gradually and SLOWLY increase the volume. Stop if your dog shows any signs of anxiety. The goal is to get your dog used to the sound of thunder, and associate it with good things. This type of desensitization may have limited success as you can only recreate the noise and not other factors like static electricity or changes in barometric pressure.
Lastly, CBD and other anti-anxiety assistants may give your pup added relief. Although consult a professional before utilizing any type of medication.