I don't subscribe to the summer/winter ammo debate - it has all the earmarks of a manufacturer created 'issue' just to sell more ammo. I carry the same ammo year round...its familiar, I know it will feed and fire, and I know where the round is going.
Lighter bullets generally penetrate less, all else being equal, which happens more when going through thicker clothing. This has been borne out many times in real world testing. If anything, I'd tend to go with a heavier bullet in winter, not a lighter one. What ballistics from Federal are you basing this on?I have used Federal Hydra-Shok 180g/.40 cal as my standard carry round because of the post that is supposed to keep the cavity clear of windshield glass and fabric, and allows for expansion (plug the cavity and it affects expansion I am told). But I recently came across and bought a case of the Federal HST 165g which hits harder than the Hydra 180g according to Federal's ballistics.