I would bring him inside, it's not fare to leave him outside, it's not like he knows whats going on. If you aren't going to be home I would put him in a safe place (inside kennel or your bedroom) and play LOUD music. Hopefully he won't be able to hear the fire works. This works for a foster dog I had that was terrified of lightning. I would put her in my bedroom and turn on the T.V. really loud, she just slept through the whole storm.
Also, people do stupid stuff on July 4th, I would never leave any animals unattended outside. Even my dog's get supervised potty visits. Teenage boys think it's fun to tie fire crakers to dog's and cats tails and watch them run.
Ashley
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