Make sure you're on the today tab and that you haven't scrolled down. Weather is at the top & I had scrolled down on the calendar and didn't realize it. At least that's what happened when my weather 'disappeared'.
Yeah, looks like i am having issues as well with notification center. I go under notifications in the settings and each app select if I want the notifications. But when I swipe down all I see the the day and calendar with events. No weather or anything else.