He'll be wearing military weight kilts right? With a pair of thick wool hose (or two) He'll surely be quite comfortable. Generally we have no meat on our knees and will handle the cold quite well. By all means wear something warm covering the groin (for those occasional chilly gusts) and protect the head. By our design, in the cold, blood will be shunted away the extremities with the major heat loss being from our head, torso and groin. Protecting those areas are the key to being warm. Being from England I've never gotten used to these bloody freezing Canadian winters (heading into my 33rd). Living on Lake Ontario it can easily get to well below -25C with the wind chill factor (cold with humidity slices right through you). I cannot remember a time feeling comfortable in those temperatures and not being kilted (bare knees and all). I guess what I'm saying is tell your friend to take along long john, heck even the red wool ones with the escape hatch in the back! Take them along for piece of mind but to not wear them unless absolutly needed. BTW silk long john are purportedly the best, perhaps can even be kept in the sporran. Now I've heard of rumours of green tights/kilt worn in the southern hemishere...