I would have preferred the next step up in warmth level but this was my error - this is just as it says - "SILKWEIGHT" which translates to pretty thin material. If you're looking for something to keep you warm in 35 degrees or less I would suggest purchasing the midweight or heavier. This undershirt would be good for high activity where you may be perspiring more than usual or like others have said, winter in a warmer climate.

UPDATE 9/27/13;
Just purchased TWO more of these silkweight shirts as they perform admirably as a base layer to these 40 degree days here in Seattle. These are great for daytime use but I do still prefer the midweight for sleeping. I'm especially impressed with "no shrinkage" after several washes, it has stayed true to size. I'm 6'2" and 225 lbs and the XXL fits perfectly.