Question

why the most parts of asia donot get rainfall during winter season?​

Answer 1

In some place this is true, but weather is a complex thing and how much and when you get precipitation depends on lots of factors. In some areas, most of the water they receive from precipitation comes in the form of snow in the winter. This is generally because these areas get moist warm air transported over the area from a body of water like an ocean, sea or lake. When this moist air moves into a cooler region, the air can no longer hold all the water and it falls as some sort of precipitation.

But in general, when very cold air moves into an area, you don’t get any precipitation in any form because the air has already lost much of it’s moisture since colder air cannot hold as much water. This means cold air tends to be dry air.