I wear my Stillwater standards with temps in the 30F range. I find them warm enough except when there is a strong wind that is actually making a windchill factor in the 20's F. I have worn my Stillwater Black heavywieght out when it was 6 F, sunny, and very little wind. It was plenty warm. Of course there comes a point where the temperature is low enough to cause frostbite to exposed skin where a kilt could allow frostbite around the knees.

So I guess it's a combination of kilt weight + temperature + windchill + amount of physical activity that would determine weather it's to cold to be wearing a kilt outside for extended periods. I would say if you feel too cold, it's time to get indoors.

Darrell