[someone123]

I don't think many people will argue that an uncovered stadium is better or that rain is rare and not worth thinking about. You have to put this in the context of the overall budget though and ask if trying to build a roof in the beginning would reduce the chance the whole thing will be built. Maybe it would be better to have no roof for a few years.

Seattle isn't very instructive here because it's a much larger city with facilities built for established and presumably vastly higher value sports teams. The stadium the Seahawks play in cost about $800M in today's dollars (CAD).