Winter season starts from mid-November and is experienced in the beginning of December throughout the country-
January and February are the coldest months. By the beginning of January high pressure gets established in Central Asia near Baikal Lake and in Pakistan near Peshawar. Indian mainland has a comparatively low-pressure region at that time. Hence cold winds begin to blow from high-pressure regions and enter India. Their direction in the country is from North-east to South-west. Thus they are called the North-east Monsoon winds. Clear sky, comfortable sunshine, very pleasant and healthy weather are some characteristic features of this season.
Temperatures are very low in northern parts and they go on increasing towards the south. The Gangetic plains have a 10°C average temperature while the Peninsula records up to 30°C temperature. Chennai experiences 24-25°C temperature at this time. Nights in North India are cold and frost occurs almost daily. But no part of South India experiences frost these days.
Western depressions of the Mediterranean origin entre India through Iran, Afghanistan and Pakistan. They cause slight rainfall in the North-western parts. Jet streams help them enter India. Jammu and Kashmir and Himachal Pradesh receive heavy snow-fall these days. Western depressions cause less rainfall but it is very beneficial for wheat cultivation in the North Plains.
The depressions lead to a cold wave which culminates in numerous deaths of the poor and ill-clad people in Uttar Pradesh and Bihar.
When the North-eastern Monsoon winds pass over the Bay of Bengal, they absorb moisture. On reaching the Eastern coasts they cause heavy rainfall. Hence, the Tamil Nadu coasts obtain rains in winter.
Characteristics of Summer Season:
Dry conditions prevail in the summer season in India from March to May. With the Sun moving northwards from the Equator in March, the temperature in India starts increasing.
In March the Deccan Plateau gets 38°C of maximum temperature. Madhya Pradesh experiences the highest temperature of 38°C in April and Uttar Pradesh, Haryana, Punjab and Rajasthan experience the highest temperature up to 48°C in May.
During the summer season, Central Asia becomes a low-pressure region. Another low-pressure area is formed near Multan in Pakistan. At this time high pressure exists on the Indian Ocean. Hence winds from the Indian Ocean begin to blow towards low-pressure areas in India.
In Kerala and Karnataka, the pre-Monsoon rains are very beneficial for mango-ripening. People call them ‘mango showers‘. Bengal and Assam also receive some rainfall through thunderstorms in the evenings. They cause havoc. They are known as “Kalbaisakhi” or “Norwesters” because they cause havoc during Baisakh month.
Dry and hot winds blow in the North-western parts of the country, increasing temperatures in the region. Exposure to these winds proves fatal. Hundreds of people fall victim to these winds every year in the plains of Uttar Pradesh and Bihar. Sometimes Madhya Pradesh is also in the grip of the heat waves during the summer season. These hot winds are known as ‘Loo’. In the north-western regions, strong dusty winds occur in the evenings. They decrease the temperature to a great extent.
Southern parts of the country remain under the influence of maritime climate. Thus they do not experience hot and dry summers.