These westerly disturbances are characterized by low pressure systems which move over northern Pakistan and head east northeastward into India. There are about seven or eight of these a month at their peak in January, but there are far fewer in October. The abundance of sunshine provides ample evidence that these systems are not particularly common in the fall. Morning fog patches are rare across northern India, but increase in frequency toward the coast at Calcutta. Thunderstorms, mostly an afternoon phenomenon, are also more common toward Calcutta.
Dust storms are an occasional hazard near the Pakistan border, but rare or unknown elsewhere.
Since the northwest monsoon is in its early stages, winds are generally light everywhere and dust is most likely to be raised by the occasional thunderstorm or front. The Bay of Bengal is famous for its cyclonic storms which occasionally strike the low lying coast of Bangladesh with great loss of life. These storms are not as common as their newspaper reputation would suggest, occurring with a frequency of less than once per month in October. Their normal path is to follow the east coast of India, curving to move inland across Bangladesh or northern Myanmar. However, a substantial fraction are not content to follow the common path, and instead head northwestward past Calcutta and into the center of the Indian sub-continent.