I believe it's an intended behavior as python's float has a limit after all. It's hard to reach it but definitely possible.
A workaround is to internally use Decimal (also take the advantage that it's implementation is now way faster) but it will cause a precision loss, and somewhat unexpected behavior.
Last thing we can do is catch that OverflowError and raise StatisticsError from exc.
I believe catching and re-raising as Statistics or just writing that it may also cause an Overflow error are the most viable ways.
Either way, I'd like another opinion before implementing either method as a patch.