Ive never had a problem with my boots being wet, on the inside or the outside.
It’s really too cold to be sweaty and unless you fell into a river, your boots aren’t going to get wet.
The ski resort we were just at, didn’t even have hair dryers for your hair!
I guess you are just supposed to sit by the fire.
If he has a runners beanie, that may fit under the helmet.
The critical point would be his ears.
We don’t generally wear a helmet Nordic skiing, but I agree it is a good idea, especially if Alpine skiing.
I’ve never had a week skiing where my boots were NOT wet at some point, and they didn’t always dry over night. Sometimes the gloves too. He needs to make sure he puts his goves out so they can dry each night. WIth three kids, we’ve sometimes had multiple dryers going at once. But don’t put them down into the boots, because that will make the dryer stop working.
I suppose if you are skiing in Western Washington, then your boots may become wet, however if average temps are in the single digits, it is not going to be warm enough for much precipitation.
You do have to knock the snow off before taking them inside, and if they are not already waterproofed, then some sort of wax preparation will help.
When we have visitors that are from warm weather this is what they borrow: ski jacket, definitely ski pants, you usually can rent a helmet and that substitutes for a hat, thick socks, ski gloves and a scarf or neck warmer, goggles are better than sunglasses but sunglasses will do.
I went skiing for the first time in 20 years a few years ago. The helmet kept my head and ears plenty warm so there was no need for a hat while skiing. Everyone seemed to be using those little foot warmer packets in their boots. I wore them the second day and they were amazing! I’ve never worn more than one pair of thin socks while skiing. A neck warmer that can be pulled up to cover the nose and mouth is definitely a necessity.
Be careful with socks. Socks especially for skiing will not only be wool, they will be fluffy and loopy on the shin side and thinner on the back with NO big seams anywhere. Seams and ribbing will get further squashed by the ski boots and could turn into bruises on your shins! Leggings for under the overalls usually are polar fleece and have no seam at the ankle. Of course, you could buy a regular pair and just rip out the seam so it doesn’t cause any trouble.