Depends on where in the south, and do you mean south as in The South or all states in the southern half of the country?
I live in Nevada, but I'm from Toronto and have lived in frigid Ottawa. I can tell you that it does get "cold" here in the southwest desert during winter, especially at altitude, although not anywhere as cold as the Great White North.

But you feel it (especially after acclimatizing for a few years) because there's a huge swing in temperature that nobody up north gets...like tonight we'll go down to about 5C but it was 18C outside today. Fifteen to twenty degree shifts between night and day are really common, so you go out early in the morning and it's cold and then by midday you're shedding layers as fast as you can.
So if you're doing something for anyone in the southwestern deserts, light versions of cold weather gear that can be part of layering would certainly be welcome.
Relative humidity makes a difference too. A lot of The South is very humid, where as out here in the southwest it's dry as a bone. So keep that in mind in terms of drying items...a thick garment that has to be kept out of the dryer won't work as well in the severe humidity of New Orleans, but it'd be totally fine in Vegas.
And when in doubt, go for something practical, like pretty cloths or a wine bag.