"Január nagyon hideg volt az idén."

Translation: January was very cold this year.

[SedatKlc]

can we take out az?

[vvsey]

Yes. But it sounds better with the "az" to my ear.
Also, if you want, you can stick an "A" in front of "január".

[Pedro771]

Another alternative: "Idén a január nagyon hideg volt."

[Sava324463]

Duolingo is persistent in not accepting similar answers...

[s7cQ5]

Pretty not equals to very?

[woarrend]

Why do we need an article? We were taught that "idén" alone means "this year".