It is interesting that people ask this as a hypothetical question, and I have seen some variant of the question in various forums sites. But there are places where you can literally walk through clouds.
The reality is that there are places where you are indeed forced to go though clouds. I have experienced this many times on Tenerife island. There is an area on the island where you have rain forest, it is very wet and it is relatively low compared to the rest of the island, up to 1000 meters or so.
You can indeed get completely wet when you walk in such an environment, and there is no way to get protected. The vapor is in the air and it penetrates everywhere. See the picture below.
My examples of walking through clouds on Tenerife
In the case of Tenerife, clouds coming from the north-west side are low, so the whole north side of Tenerife is very green. Clouds get to the island and they are stuck there. So plants get lost of moisture even if it does nor rain.
The top picture above shows one example from my Chamorga to La laguna tour, a walk of over 35 kilometers. So the picture is not sharp but what you see as a fog is in fact a cloud.
In the picture below you can see my wet arm and my watch that measured altitude, so you realize it was very low, only 740 meters. that is how low those clouds can be.
When you walk though such an area, you get wet from the plants around because everything is wet.
But I was wet even before getting there, the top picture is from a spot close to the beginning of the tour where I had a clear path, and I was not touching bushes around. I became wet from the air itself because it was full of cloud vapor.
The picture below shows a part from the same tour where I had a walk along the road. So what you see here is not a fog, this is the cloud. The elevation here is probably around 850 meters or so.
In some occasions I would walk for hours in such an environment and I can tell you it looks like walking in the fog. If you follow the link you will realize that regarding moisture, there is no difference between a fog and a cloud.
Normally the vapor in a cloud is in small quantities per any unit volume, but in time you get completely soaked.
This was exactly the case with me. I did not mind because it was not cold, but in some situations I could not even use my camera because it would have moisture inside. So many photos were actually low quality and I could not use them. This one below is from my tour through Pijaral rain forest.
The same happened once also when I was descending Mount Teide after watching sunset from the summit. The summit was far above the clouds and the sky was clear.
But on the way down, I was passing through a cloud area which was in the elevation range from around 3000 meters all the way down to the car parking at 2300 meters. The picture below shows what I had in front of me.
Because of the moisture, my torch stopped working. I was so disappointed with it. So I was walking a couple of hours in a complete dark.
What is really in the cloud?
There is usually moisture in the air and its amount depends on a variety of conditions. But you have it far more in a cloud. These tiny vapor droplets are micron size and they are carried by the air. If there are contaminants in the air, then there is a higher chance that these droplets attach to them and they can grow.
They can grow also when they merge with other droplets in the air, and in this case they are not suspended by the air any longer. This is in short how we get rain.
There is no basic difference between a cloud and a valley fog. But in the case of fog, pollutants can present a real danger. I was reading an article about an accident in Belgium almost a century ago. Such a vapor was condensing in a highly polluted air, and more than 60 people died because of pollution. They were simply inhaling such a vapor with pollutants.
As mentioned above, the same nucleation catalyst acts in a cloud as well. I have read somewhere that people spray clouds with some stuff to enhance this effect and to get rain.
Back to my long walk mentioned above. It is interesting that I did it successfully and got to the tram in La Laguna that was taking me to Santa Cruz. But while sitting in the tram, I collapsed and fainted for a few moments. Luckily, I was sitting so nobody noticed, but I did not feel great really. Perhaps I had too much stuff in my lungs that day, but I shall never know.
Catching water from the fog and clouds
Did you know that there are dry areas where people catch water from the fog? I have read about such places in Peru, you can search for fog catchers. Here is a video about this:
In conclusion, you can indeed get completely wet when you walk through clouds even if you formally do not experience any rain. This walking in clouds is not a hypothetical thing, it is real, and I have experienced it in the mountains numerous times. Some of examples are mentioned above but I have them many more.
Thank you for reading. Let me know if you have questions, there is a comment box below. Bookmark this site and keep as a reference, I hope you can see some value in it. Have a nice day.