Some of these places in the Southwest not only get into the low 20s but you could also get into a heavy snow in some areas. Do you know how to drive in snow pulling a TT? Speed/time/distance. Always error on the safe side and plan for more 'time' than you normally would. Think about your tow vehicle as much as your TT. It should be ready for 'winter' conditions.
2013 Forest River Salem Hemisphere SBT312QBUD
2001 CrewCab F-250 7.3 PowerStroke Diesel
SuperChip, BTS transmission, 6.0 Trans Cooler