Hi JCWohlschlag,
I have carried road flares in my truck kit for years and do know that if they sit in the bottom of a damp tool box of a long time (might have been years) the fusee expands and the outer casing splits (big mess).
I will test the waterproofness of a road flare this afternoon and post the results.
(LOL, I can hear the fire trucks already).
Mike