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. The characteristic features of this season are afternoon dust storms and 'Loo' which is a hot dry wind which blows during May and June mainly over the northern plains. These winds cause heat stroke resulting in deaths of hundreds of people every year. The day temperatures at times rise above 45°C in some north-western parts of the country.
The wind direction is variable during this season. The weather conditions are generally hot and dry throughout the country. However, dust storms cause drizzle in Northern Plains. Light showers are also experienced in Kerala, West Bengal and Assam. In Kerala, these pre-monsoon showers are popularly known as “Mango Showers”. In West Bengal and Assam, they are called Northwesters or Kal Baisakhi. Sometimes, due to high velocity of winds these Northwesters cause heavy loss of life and property.
The main characteristic features of hot weather season are hot and dry weather, blowing of Loo - a hot dry wind in northern plains, afternoon dust storms, sometimes causing drizzle and mild showers in Kerala (Mango showers), West Bengal and Assam (Northwesters / Kal Baisakhi).