poly pro shirt w/Bare T100 is fine for me from maybe 53 on up.
Temps below that I layer on extra stuff: Poly pro long johns, long sleeve cotton shirt, and sometimes and additional Tshirt. I wear the cotton stuff between the poly pro stuff and the T100.
Temps below that I layer on extra stuff: Poly pro long johns, long sleeve cotton shirt, and sometimes and additional Tshirt. I wear the cotton stuff between the poly pro stuff and the T100.