What temperature condition requires the wing anti-ice to be turned off just prior to takeoff?

The requirement to turn off the wing anti-ice prior to takeoff is associated with temperature conditions where ice may not form due to warmer temperatures. Specifically, when the outside air temperature (OAT) is 5 degrees Celsius or colder, there is a risk of ice forming on the wings if moisture is present. However, if OAT is above this threshold, the likelihood of ice accumulation is significantly reduced, making it safe to turn off the wing anti-ice system.

This is crucial for ensuring optimal aerodynamic performance during takeoff; having the anti-ice system activated in warmer conditions could lead to unnecessary weight and potential operational inefficiencies. The other options reference conditions either of visible moisture, which might necessitate the use of anti-ice, or general weather conditions that do not specifically address the temperature factor relevant to activating the anti-ice system.