Final answer:
The stage direction of 'lightning, thunder, and the sound of whirling wind' in Act 1, Scene 3 of Macbeth contributes to the scene by creating an ominous mood as Macbeth and Banquo see the witches.
Step-by-step explanation:
The stage direction describing 'lightning, thunder, and the sound of whirling wind' most contributes to the scene by creating an ominous mood as Macbeth and Banquo see the witches. The stormy weather in Act 1, Scene 3 of Macbeth suggests that something dark and mysterious is about to happen.
It sets the tone for the appearance of the witches and foreshadows the evil and chaos that will follow.