We have done just as Dutchmen posted above for the past 17 years. We traveled from Michigan to either Florida or Texas most years.
Last year the temp was 14 below zero when we left and was the same for the next day. :E . Those temps were abnormal though - usually just in the teens or single digits.
I would just pack as normal and when you get to warmer temps, de-winterize and enjoy the use of your trailer. Just realize that things are going to freeze inside both the trailer and the fridge unless you have the heat on all the time while traveling. We never ran the heat while moving and didn't have any problems. We stayed in motels until we got to where the temps were more reasonable. Last year was not normal though for temps.
Barney