Water is the obvious first problem to consider.
The easiest solution to freezing water is to bring water containers inside, or covering them.
Do remember to insulate the pipe into the caravan as well as the barrel.

Be careful with submersible pumps as they can retain water inside and therefore be at risk of frost damage.
Keeping your Aquaroll topped up helps as a bigger volume of water will take longer to freeze in cold conditions.
If you fancy getting away a lot in low temperatures, it maybe worth considering adding an on-board water tank.
Waste water can also be a problem, as we found when we toured Europe one December.
To help with this problem, we insulated the pipes under the caravan.
We do not recommend using antifreeze as this attacks plastic.
If sinks and showers block up, we found a hot salt mixture did the trick.
Plus, as we keep saying, remember to drain everything.

Although caravans stay warm the outside does not, so condensation forms on the windows.
This is a big problem first thing in the morning, so it is worth putting them on vent,
or giving them a wipe down with a chamois leather.

Use propane gas instead of butane, as this cannot operate at lower temperatures.
Propane will work at -40°c. In the UK propane is a mixture of propane and butane,
but as you visit colder countries the percentage of propane will be higher.
Adversely, as you head south the amount of propane will be less.

When temperatures roughly drop below 8°c, fridge vents can be restricted.
Each manufacturer is different, so check your handbook.
These restrict the free flow of cooling air but permit unrestricted venting
of exhaust gases.

It is important to ensure that you have a good quality battery that is fully charged before your outing.
Cold temperatures can slow down the reactions in the battery and result in lower battery capacity.
A flat battery can freeze.

Once again we return to tyres, but it is never more important than when travelling on icy roads.
You can consider winter tyres, or all-season tyres are a compromise.
Sometimes marked with an M + S (mud and snow) symbol.
Experts recommend a minimum of 4mm depth of tread for winter motoring, and certainly no less than 3mm.
Check your tyre pressure because they lower when cold.

Our only other piece of personal advice that we learnt in Switzerland, when night temperatures dropped to -14ºc,
is spraying some WD40 into locks, not forgetting the front locker box.
If you regularly go away in the winter, this can be done once a year.
Also silicone all the doors and window rubbers to stop them sticking at low temperatures.