They are very light weight cotton; on the order of T-shirt weight fabric; if just a cover up and you're in Warmer climate, they should be fine; if in a colder climate might not be enough warmth. And, if you run a warmer internal core temp, it might be not enough, too. Comparison, I have thicker weight Russell Athletc bottoms and they're just a bit too warm for me...but in San Diego. the temp. now is 61 deg F. and I'm sensitive to heat so have to adjust attire all the time.