the outer portion of the wing was coated in frost, with a visibly rough texture to the surface.
I was hoping the frost would melt in the sunlight as we taxied to the threshold, but there was still some remaining as we began the takeoff roll
From the 737 Supplementary Procedures section Adverse weather.
Quote: "Take off with light coatings of frost, up to 3mm in thickness on lower surfaces due to cold fuel is allowable; however, all leading edge devices, all control surfaces, tab surfaces
upper wing surfaces and control balance cavities must be free of snow, ice and frost".
Seems someone was pushing his luck?