What is the cloak that Naruto wears in the snow?

The Seventh Generation's jersey.

According to Naruto's official website, Naruto has been wearing a cloak since he became Hokage. This cloak is the Seventh Generation's robe.

Uzumaki Naruto, the male protagonist in the Japanese comic "Naruto" and its derivative works. A ninja from the Hidden Leaf Village of the Land of Fire, the son of the Fourth Hokage Namikaze Minato and Uzumaki Kushina, the reincarnation of Asura, the second son of the Six Paths Sage.