I live in NY and have 4-5 months of winter. I usually go through a touchless laser car wash when I want to clean the exterior...preferable doing it a day that is above freezing (if possible). Doesn't do the best job, but it's still pretty good and I like to at least get the salt off the paint and from underneath.

I imagine having a fresh wax done right before winter will result in the laser car wash doing a better job (will do that next winter).

 

I'd think a good sealant and wax sometime around mid-November would be a good idea here in Northern VA. It doesn't really get cold until December here anyway.

I have yet to find a real touchless car wash anywhere around here, but I haven't looked all that thoroughly.