I understand it is warm in much of North America currently but you would never know that from temperatures in the part of the world that I inhabit. Winter has returned here and out came not just the gray flannel suit but its vest, an item I doubt if I had worn all season.
Vests do double duty with single breasted suits. They provide a different look periodically as well as a significantly warmer one. Since flannel is a little more casual than worsted, mine has lapels, a country detail that in this case is at home in the city.
With the suit is a light blue shirt with white collar and cuffs, a white linen handkerchief, brown quarter brogues and a navy Cappelli necktie with white and brown figures to pull it all together. That is nearly as formal as gray flannel can get - had I wanted to dress it down I would have worn a checked flannelette shirt, full brogues, a cashmere necktie and a silk pocket square.
It will be chilly again tomorrow and I once again I will head down to the storage closet for something to wear. That tempting row of warmer weather clothing that I optimistically brought out last week will continue to hang undisturbed.