Head and Shoulders is great to use for all seasons.  I used to only use it in the winter because the weather is so dry here but it is also great in the summer to maintain my color treated hair.

I strongly suggest using it in the winter months as we tend to wear darker clothes which often shows off the flakes.  You no longer have to be the one that people stare at because of the flakes on your new black sweater...just use Head and Shoulders.  Love it and can't live without it.