The road surface can get quite slick even if ambient temperature is above 32F. This is probably the reason why BMW's warn you if the outside temperature is 37F.
You can't tell by looking at the road surface whether it's slick or not in some cases. Years ago, I crossed a bridge late at night (temp in the upper 30's) in a Corvette (yes, various substances had been consumed
) and instantly found myself going lock to lock the whole length of the bridge (all effects of said substances being instantly erased by a large hit of adrenalin at this point) as I corrected, corrected, and corrected again. Mercifully, I managed not to hit the bridge sides, though I did slide down an embankment on the opposite side.
When I tried to walk into town I almost fell down because the surface was so slick, though nothing was visible. Keep that DSC on, and don't expect any performance tire to handle snow or ice.