Is Icirrus City only accessible during winter?

Question

(B2/W2 btw!!)

I think I've read somewhere that Icirrus City is accessible only during the winter, but I'm not too sure

Answer 1

There are a couple snowdrifts in and around the city that only appear during winter, and which provide the only means of access to get up to a particular house or to a high ledge, but the city at large can be crossed during any season (in fact, the wild Pokemon there can be found in every season except winter, as they're constrained to appearing in pools of shallow water which will be frozen over.

Answer 2

No there's nothing as such!
It would make the game too long. If you reached that part in March will you wait for few months to just complete the game? Game freak wouldn't want that until unless it wants to lose fans.
Also there's nothing as such is bulbapedia.
Hope I helped!