In the context of local storms of hot weather season, Nor’Westers are:

The correct answer is the dreaded evening thunderstorms in Bengal and Assam.

Understanding Nor'Westers (Kalbaishakhi):
During the hot weather season (local summer) in the Indian subcontinent, intense heating of the landmass leads to the development of localized low-pressure areas. These conditions draw in cool, moist winds from the Bay of Bengal, resulting in violent local storms.
In Bengal and Assam, these dreaded evening thunderstorms are known as Nor'Westers (or Kalbaishakhi in Bengali, meaning the calamity of the month of Baishakh). They are typically accompanied by torrential rain, strong winds, and sometimes hail.

Analyzing the other options:
1. "a nearby wind that blows coffee flowers in Kerala": This refers to Blossom Showers, which help in the flowering of coffee plants in Kerala and nearby areas.
2. "the hot, dry and oppressing winds blowing in the Northern plains...": This refers to the Loo, which is characteristic of the summer season in Northern India.
3. "the pre-monsoon showers that are a common phenomenon in Kerala and coastal areas of Karnataka": These are commonly known as Mango Showers, as they assist in the early ripening of mangoes.