Western Disturbance is an extra- tropical storm that originates in the Mediterranean region. It is driven by the Westerlies (prevailing winds that blow from the west to east) It is an area of low pressure that is responsible for bringing in sudden rains, snowfall and fogs in north-western India. The recent Western Disturbance is responsible for an increased amount of snowfall in J&K, Himachal Pradesh and Uttarakhand and the rapid dip in Delhi’s temperature.