As Ned Stark warned on the very first episode of "Game of Thrones": "Winter is coming." Well, it's Season 7 and winter is definitely here. But as an eagle-eyed fan on Reddit discovered, winter's slow, but steady arrival was teased in the opening credits of the show.

Redditor RohitMSasi pointed out that the opening credits of the Season 7 premiere showed the seas around the Wall had turned into ice. And yes, as you can see, the sea to the East of the Wall appears to have frozen over — possibly enough for the army of White Walkers to possibly traverse:

Game of Thrones

But Collider took it further and examined the opening credits of all previous seasons and realized that the credits have been showing winter's encroach all along.

Here are the credits to the pilot episode. Look at how the seas on both sides of the wall are deep blue. Also note the absence of any icebergs:

Game of Thrones

In the Season 2 premiere credits, not much has changed. Notice, though, how much green there is still around the coasts:

Game of Thrones
But in the Season 3 premiere credits, that green is almost totally gone. The sea to the west of the Wall — aptly named the Bay of Ice — looks, well, a lot icier:

Game of ThronesCollider indicated that land mass to the east of the Wall were icebergs, but it could be that the people who designed the credits belatedly added the island chain of Skagos, which lies in the Bay of Seals to the east of the Wall. In any case, note how brown that land mass looks.

Jump ahead to Season 5 and that land mass is much whiter:

And here is the Season 7 premiere credits again, to compare. See how little blue there is in the seas on either side of the Wall:

Game of ThronesNed Stark was right about this, at least — winter was coming. It's definitely here.