Longjohns, common colds and arthritis

My father rarlely catches a cold.  He also has a habit of only drinking warm water.  I found out through the internet long ago that virus multiply fastest at around 32 degrees Celsius.  I also read recently that our immune system is less effective at temperature lower than 37 degrees Celsius. No matter what the reason, I am going to keep warm this winter and use my longjohns; as 1/3 of an adult body surface area is in the legs.
The other reason I use longjohns in the colder season is to prevent inflammation in my knees.  I think the immune system can be perturbed by infections and temperature fluctuations. I think that might be the reason for the experience of catching colds, body aches and arthritis flare ups that is more prevalent in cold and damp weather and climates.  I think the reason damp weather provoked arthritis flare up may be due to the fact that humid air is more conductive or provides less insulation against the cold ambient temperatures.

One other cold prevention strategy I suspect based on my experience is the sufficient consumption of vegetables.  In a large group of Sudanese children, researchers found that those with the highest intake of both green leafy vegetables and non-leafy vegetables had about 25-45% lower risk of experiencing diarrhea, cough with fever, or measles[3]. Results were adjusted for socioeconomic factors and overall nutritional status.