Our daughter is a slight salt waster and she melts in the heat.  Our biggest challenge this spring was her playing travel soccer in the heat.  We ended up doubling her cortef for the 70's weather and tripling in the 80's weather.  Even then she might not hold up well.  Our endo says she can do competitive sports even in the heat, so we are trying to manage the CAH without holding her back.  We use a lot of gatorade, but ended up with 4 cavities.  Make sure they at least rinse with water if drinking a lot of it.