I do not think that the atmosphere in Macbeth necessarily helps Macbeth to make the decision to murder; however, I do think that the atmosphere symbolizes and characterizes his decision. For example, when Macbeth is in the midst of deciding whether or not he should murder King Duncan, he hallucinates a dagger. The atmosphere present here at the beginning of Act 2 is one of confusion and mystery which characterizes Macbeth's state of mind and his inner conflict but does not necessarily push him towards making the decision to murder. Macbeth is persuaded by his own selfish ambition and the chiding of his wife to make the decision to murder for the crown. So the atmosphere is suggestive of Macbeth's state of mind and does not influence him to actually make the decision.