Inconsistent weather...
...So, of course, they want to make this dark and gritty. Very dark. (Is there any other way to portray Gotham nowadays, other than very dark and either overcast or rainy?! The original 50's TV series wasn't dark/rainy at all!)
So pay attention while watching: when they're downtown or in the bad areas of town, it's always rainy and/or dark. When they go to a rich person's house in the Gotham suburbs...it's simply a bit overcast, never raining. So the weather gets better in Gotham if you live in a good neighborhood?!