As has been stated previously, humidity is the biggest problem.
Here are some things you can do to avoid those problems:
A) Keep your laptop sealed in an air-tight bag when it is, or is going to get, cold.
Do not open up the bag until the laptop has warmed up to close to room temperature. If the room is only 40 degrees F that is OK because everything else in the room would have already condensed whatever excess humidity out of the air already. (Not ALL the humidity, mind you. Just down to a point where the laptop would not get condensation in and on it.) Even then, don't open the bag until you are getting ready to turn the thing on.
I know, it is hard to charge a laptop in a sealed bag without some ingenuity.
B) Keep your laptop, and other electronics in a small cooler. (No ice or food or anything. Just a dry cooler with your electronics and maybe some padding in it.)
This will keep them from getting nearly as cold or hot as their surroundings. A lot of photographers keep their equipment in coolers to protect them from the heat in the trunk or just the freezing cold. In the winter, if you put your laptop in the cooler just after you turn it off then the residual heat will keep it relatively warm for some time. (DO NOT leave it on in there!) This will at least keep it warm enough to prevent condensation. You can even carve a little notch in the edge of the cooler for the charging cable. Again, don't pull it out until you plan to turn it on.
Of course, if your van or RV living space is well insulated and it never really gets down below about 40 or over 100 in there, then you are probably fine without doing anything.