You are kidding right?
Or is this one of those questions on the Menza test?
The speed of light is the speed of light! Right? I am sure, are you?
If you're question was serious, and not a trick question, then your question was misstated.
The speed of light is always the same.
The amount of time it takes an electric discharge to travel from point a to point b will always be effected by the path it takes, that being the path of least resistance to it's contact with the ground.
I hope that my answer is correct, without incorrect assumptions.
I hate the word assume. It always makes an ASS of U and ME.
Have a great day.