Saraka2008 is right there is different additives in summer gas and winter gas, though I am not sure of the difference in the additives. I add SeaFoam every so often to help keep things cleaned out.
As for the chill speaking as somebody who grew up in Michigan, married a Georgia peach then moved to Ohio. I can tell you, your body becomes acclimated to certain temperature. Since moving back up north after living down south for 14 years, I am now officially a freeze baby. Below 60 and I am in a jacket. In Georgia I worked outside as a Conductor on the railroad, it was down into the 20's for about 1 month but 40's during the day. Sweet Tooth is spot on the humidity makes it feel even colder. I am ready for summer already.