Tonight the weatherman announced there was a chance of snow "early on on Wednesday." Seems there's an extra "on" in there. I've heard this construction in conversations but not in writing, so I assume it's a faily common oral redundancy.

It's a natural consequence of joining the colloquial "early on" (You'd better come early on or we'll miss the start.) to "on Wednesday".

I've heard it too. Maybe it makes a little more sense written with a comma "early on, on Wednesday".

I think it's better to just remove the second "on."