By the end of February the temperature starts rising. So from March to May it is hot weather season.
The apparent movement of the sun towards the north increases the temperatures in the northern plains. As a result, the spring sets in soon giving way to the hot weather season which lasts till end of June in this region. The temperatures increase northwards and reach around 45°C in mid May in most parts of the northern plains.
In Northern plains, an elongated low pressure (monsoonal trough) is created, which extends from Jaisalmer in western Rajasthan to Jharkhand and parts of Odisha to the East. However, over Indian Ocean south of the equator high pressure belt begins to develop in this season.
During summer, very hot and dry winds blow over North Indian plains. They are locally called Loo.
This is also the season for localized thunderstorms, associated with violent winds, torrential downpours, often accompanied by hail. In West Bengal, these storms are known as the Kaal Baisakhi (calamity for the month of Baisakh). Towards the close of the summer season, pre-monsoon showers are common, especially in Kerala and Karnataka. They help in the early ripening of mangoes, and are often referred to as mango showers.