Fireworks looks like your fingers are making fireworks in the sky. Start with your hand as a fist and your index finger extended. Move your hand upward and then open your hand, letting your fingers radiate outward as if they were exploding fireworks. You can repeat this motion with alternate hands.
Prepare your baby for an upcoming fireworks show by showing her pictures and videos of fireworks along with the sign. This will let your baby build up some anticipation for the event, and also get him comfortable with the idea of 'fireworks' so he will not be scared when he sees them live for the first time.
Teach this sign in preparation for the 4th of July and New Year's Eve. If needed, illustrate the sign by showing your baby videos of fireworks.