..what kind of impact would the venturi have on airflow temp in a light single?
That is well answered above. Also pertinent is what impact the airflow temp has on the venturi. Carb ice forms on the downwind end of the venturi and disturbs its aerodynamics, causing the airflow to draw less fuel, to the point of starving the engine. Carb heat and full rich are the correct responses. A few cc of ice will make you sweat - when the fan stops.
Legend has it that carb icing occurs at partial throttle. Not always.
The only time I encountered carb ice in the 150 Franklin engine in my Bellanca Cruisair, was full throttle, leaned, at 5,500 feet over the former atomic power plant near Portland, Oregon. The icing remained almost to landing some 20 miles away.
The only time I encountered carb ice in the later 165 Franklin with larger carb, in the same Bellanca, several years later, was at 1,500 feet, near full throttle on climbout from KSAN. The rough running took me by such surprise that icing didn't occur to me. In fact, I was rehearsing my mayday call for return when I remembered what an ATC guy had told me over coffee. They have an emergency checklist in the tower cab, with basic instructions like full mixture, fullest tank, carb heat(!)...
GB