We're NE of you in SW Michigan, and made MANY trips south in the winter. My best advice? Be flexible; and set your RV up for easy winterization with a 3-way valve attached to the pump, so all you have to do is throw the water heater bypass switch (drain the heater, of course); flip the valve; and let the pump send antifreeze through the RV using a tube stuck into the antifreeze bottle. A few trips, we would re-winterize if the cold temps caught up with us - it was about a 10-minute process (no big deal)
And then, watch the weather - wait for a few clear days.
We would un-winterize when the nighttime temps stayed above freezing, wherever that might be. Until that point, we still used the RV, by using bottled water, and flushing with RV antifreeze. Reflectix insulation cut to fit our windows kept us toasty - even in single-digit temps (although in extreme cold, we put NO liquids down the drains).
Something to remember: even if you leave during "nice" weather, there will still be roadsalt residue on the roads - rinse the underside of your RV thoroughly once you get far enough south.