One of the cool things about Google Now is that Mountain View can tweak the way information is displayed by flipping a switch on its end. No action on your part is required to make the cards better and more informative. To that end, Google has been testing an updated version of the weather card for a few weeks, and judging by the barrage of tips we're getting, it looks like it's rolling out now.
Left: New, Right: Old
The new card lists the weather in nearby cities as stacked lines in a single card. The old style was to have multiple cards when necessary, but would usually default to only showing the weather in one location. However, the new card doesn't have forecast information immediately visible. It's one step further away with the new card.
This change seems to be rolling out to the general public, but it's far from universal right now – I don't have it on any of my devices yet. Go ahead and refresh Google Now and see what you get.