A flood I would understand as it would flood down and inside, but the fact that it's underground would protect it from such elements.
If I were in Hannah's shoes, I would've gone back to the original shelter. Most will let someone who's homeless sleep in the office/lobby if all beds are full and they can't find one for them anywhere else.
If I remember correctly they do that when it's deemed unsafe both for the staff that run the subway to get to work, and for anyone else out on the roads (as some people even when taking public transport need to be on the roads to actually get to the subway if they don't live by a stop) and the general idea of all the closures during huge storms is to get everyone but emergency vehicles off the roads, and closing public metro helps with that.
Just saw it today and the sign said something about reconstruction
shareNot true....I work at a shelter and we are not allowed to do that.