Airbus can have hoarfrost on the top surface of the tanks with cold soaked fuel, even on a 20C day, and many A types are approved for takeoff in that condition as the chief pilot of a former employer advised me after I put in a query. Of course lift from that small section of the wing is next to nothing, but the rest of the wing still works.
Dry snow accumulation on an already cold wing during taxi with air temperature below 0C will blow off.
Other cases can be problematic.
There are combinations of wing, air and precipitation temperature that demand de-icing with a holdover time, generally when the precip sticks to the wing. I remember being seated over the wing. We were de-iced at the gate in ORD and joined the conga line. In the early takeoff acceleration, the entire blanket of snow slid off the wings and joined the pile left by departing aircraft.
Everything above 0C is good as is everything well below 0C.