Flag is just like Connecticut is now - Cold... Very... Very...Cold... (wonder why I moved?)
First question is why type of Oil are you using? I have noticed that if I didn't change over to the 5w30 from the 10w30 I was using, then my engine did seem a bit rough. (not that it should hurt anything, but it was noticeable.)
Could be many other things I know, but that is my 1st thought.. my 2 cents if you will.
Side note- when I changed over to 5w30 for these few 'cooler' months here in the valley, I noticed my car was acting Diff... so - who knows....