For many families, some part of the late fall and winter involves a trip to the south. It might be to Disney Land or Disney World, depending upon where you live. It might involve the several Gulf States trying still to recover and rebuild finances and resort travel from the BP oil blow out.
In any case, you can easily shove a little freshwater tackle into the car or an airline travel bag. Realize that for freshwater fishing, you probably already have the tackle you need, with perhaps only a few adjustments. For example, if you are a Maine smallmouth fisherman, you have the rods, reels, lines and lures for largemouth, a more southern fish related to smallmouth.
Admittedly, the largemouth of south Florida or the swamps around the Gulf states or in lakes of San Diego are larger and tougher than the river smallmouth of Maine, but you can still fish easily with your tackle. Most of us have a range of tackle of all types. I have fly rods of 4-weight for light trout fishing, and some of 10-weights for big pike and yes, even saltwater fly fishing. The same applies to casting and spinning tackle, so that I can adjust for any part of the country the tackle needed for the fish and conditions.
If there is any change you might want to make, it could be in the line category so that you can cope with the heavy weeds of the south, the tules of the West Coast, the cedar knees of the Gulf and such. If it is too light, spool off the line you presently have on spinning and casting reels and reline with heavier pound test perhaps in the 15 to 20 pound range. If worried about line capacity, go with some gel spun line that is thinner for the same tensile strength as mono. Add a heavy mono leader to the end so that the opaque line does not show.
If fishing the southern left coast for the big bass around San Diego, keep the same thinner line on your reels, but when you get to your destination, visit a local tackle shop and add some of the big lures that serious anglers use for this bass fishing for the big boys.
For fly fishing, take the heavier tackle, such as outfits for 8 through 10 weight lines. Make sure that you have high quality and enough Dacron or gel spun backing on the reel under the weight forward fly line. Use a heavy short leader of about 8 feet length. For best results, both for some local tips and to cement relations with a local fishing guide or tackle shop, buy your leaders or leader material on site.
Realize also that lures, bug and flies are often best bought on site, buying them locally to gladden the heart of the local tackle shop as well as helping him feel comfortable about divulging some favorite spots and techniques for your winter trip. After all, with good results and catches, you might come back the following year.