The correct answer is Western disturbances. Explanation & Key Takeaways: • Western Disturbances are responsible for the rainfall during winter over the northwestern part of India. • The Western Disturbance originates in the mid-latitude region near Europe and the Atlantic Ocean. • The low pressure builds up over the Mediterranean Sea and moves over Iraq, Afghanistan, and Pakistan before entering India, and contains substantial amounts of moisture. • When these low-pressure systems reach the Indian subcontinent, they are blocked by the Himalayas and rain as snow over the northwestern plains and the higher reaches of the western Himalayas. • After precipitation over northwest India, they weaken and are devoid of moisture, they blow as dry winds that form dense fog over the northern plains of India. Related Concepts: • The period June to September is referred to as the Southwest Monsoon period. • Southwest Monsoon period is the principal rainy season for the Indian subcontinent. • This is the summer monsoon period where the southwest monsoon holds away over the country. • The whole country receives nearly 75% of its rainfall during this period.