Towing in winter, even a properly prepared 4 season trailer can be an adventure. When we left the Finger Lakes, the temps were in the upper 40s and sunny, but as we went south and west it got colder with every stop. First couple of days in Natural Bridge, VA saw temps down to 20 and light snow. Then in Cumberland Gap, TN, there was 6 inches of slushy wet snow. A few days later at Mammoth Cave, KY was the deep freeze: temps down to -5 F and a solid 6 inches of crusted over snow at the campsite. Our plans to go down the Natchez Trace Parkway were destroyed by ice and snow on the Trace, downed trees and ice, and more freezing temps. So we cut across Arkansas on the interstate and saw more snow in Little Rock. We tried to not tow when it was actually snowing, and were for the most part successful until Colorado. Most crazy: By the time we got to San Padre Island, temps were above freezing, but Texans were still panicked. Except for one night when I forgot to open the valve to the reserve propane tank, everything went well. That night we woke up to 20F in the trailer. Things were nice and warm in an hour after I opened the gas valve. And we saw lots of lake effect snow again on the way home in Ohio and NY.
The trailer is a Grand Design 18 footer that was sold as four season prepped. It came with good insulation in the walls, floor and ceiling, underbelly heating provided by ducts from the furnace, and twin oversized 30 gallon propane tanks. I added 12 volt heaters for the fresh, gray and black water tanks, (these can run when being towed) and a 120 volt 1,500 watt electric heater to the a/c unit. When temperatures are below freezing, and the plumbing in the trailer is not prepped for winter storage (cause you are using it!), you need to keep the 12 volt tank heaters on and run the furnace on low, when running down the road. You top off the propane at every campsite. And when we are hooked up to electric, we use the electric heater as well as the furnace, to save on propane.
We are planning on a similar trip starting in March this year.