Question

What is the role of "Western Disturbances" in the India

Answer 1

Western disturbances is the term used to describe an extratropical storm that brings sudden winter rain and snow to the northwestern parts of the Indian subcontinent. This is a non-monsoonal precipitation pattern driven by the Westerlies.
It is responsible for the change in temperature in India.

Answer 2

first we have to understand what is a western disturbance?   While a Google search would show that a western disturbance (WD) is an extra-tropical storm which originates in the Mediterranean region, the meaning of WD lies in its name. 
effects of western disturbance in india
According to IMD, the severe rain this year is the result of the confluence of western disturbance and easterly wave from the Bay of Bengal. Easterly wave, or Easterlies, blow throughout the year from east to west. The confluence of the two winds happens throughout the year, but the results vary. They generally bring rain only to the northern part of the country but this year states in central and south India also received rain.
  Western parts of Madhya Pradesh, for instance, received over 2,025 times more than usual rainfall during March 1-18