He's 5 year old so get a nice book on the weather and information on how Thunder and Lightening Happen, sit him down and explain to him how it happens with the Aid of the Book.Ha anyone in the Family made him react this way by saying they are scared of it and he is copying and doing the same thing,Alot of small kids dont like the Bangs in Fireworks, just let him be like that ,I would keep him with you but just let him read or do something else its not a punishement its his choice,