Chillai Kalan begins on 21st December and ends on 31st January.

It is the 40-day harshest winter period. During these days a cold wave grips the region and the temperature drops considerably.

It often leads to freezing of water bodies including the famous Dal Lake. Some of the water supply lines in the valley also freeze.

The sun is rarely seen during this period and the chances of snowfall are highest.

Chillai-Kalan is followed by a 20-day long Chillai-Khurd (small cold). It occurs between January 31 and February 19 and a 10-day long Chillai-Bachha (baby cold) which is from February 20 to March 2.

In the past couple of years there has been more snowfall and colder temperatures during Chillai Khurd and Chillai Bachcha than during Chillai Kalan.