I went riding at 5AM with no warming sunlight with wind and it was zero degrees celsius.
Underneath I had a baselayer and a shortsleeved jersey.
Needless to say I did not feel any windchill what so ever.
During a rest period I did feel some chill, but once you're moving the jacket kept me feeling nice and insulated from the climate.
Any weather above 10 degrees...I might not wear it in favor of the Castelli Mortirolo in fear of cooking underneath.
But as in all functional clothes it needs to fit nice and snug in order for the materials to function properly. The fit was standard Castelli...I wear L jerseys and a Large fit fine.
This jacket works PERIOD!!!!