Unless the weather forecast changes, there could be a lot of empty seats. You don't have to be too deep in the wilds of Greater Manchester to be having concerns about taking the car out (and getting home again afterwards).
That said, I think the only grounds for cancellation will be safety concerns around access to the stadium itself. There, oddly enough, the fact that the whole area is already a nightmare of roadworks that have even blocked some pedestrian routes might work in its favour. Less roads left to close, and smaller areas to clear!