The climatic conditions of southern India are a bit different from those of the northern parts with respect to temperature, rainfall and commencement as well as duration of different seasons.
The places which are closer to equator have high temperature. As one moves towards the poles temperature decreases. India is located in Northern hemisphere roughly between 6°N to 37°N latitudes.
The Tropic of Cancer passes through the middle of the country. The southern parts being closer to the Equator, experience high temperatures throughout the year. The northern parts on the other hand lie in the warm temperate zone. Hence they experience low temperatures particularly, in winter. Water bodies surrounding peninsular India make climatic conditions mild along the coastal areas.
Southern or peninsular India is surrounded by the Arabian Sea, the Indian ocean and the Bay of Bengal, hence the climate of coastal regions of India is equable or maritime. Due to moderating influence of the sea this region is neither hot in summer nor very cold in winter.
Contrary to this, the climate of the regions located in the interior of the country are cut off from the oceanic influence. As a result, they have an extreme or continental type of climate.
The Himalayan and adjoining mountain ranges which extend from Kashmir in the Northwest to Arunachal Pradesh in the Northeast, separate India from the rest of Asia. These ranges protect India from the bitterly cold and dry winds of Central Asia during winter. They also act as an effective physical barrier for the
rain bearing southwest monsoons winds to cross the northern frontiers of India.
Thus, these ranges act as a climatic divide between Indian Sub-Continent and Central Asia.
This system consists of monsoon winds, land and sea breeze, and local winds. In winter the winds blow from land to sea so they are cold and dry. On the other hand, in summer wind blow from sea to land bringing the moisture along with them from the sea and they cause wide spread rain in most part of the country.
The changes in the upper air circulation over Indian landmass is cause for sudden outbreak of monsoons in India. Jet streams in the upper air system influence the climate of India in the following ways:
(a) Westerly Jet stream
During Winter, at about 8 km above sea level, a westerly jet stream blows at a very high speed over the subtropical zone. This jet stream blows eastwards south of the Himalayan ranges along 25° N latitude. This jet stream is responsible for bringing western disturbances from the Mediterranean region into Indian sub-continent. Winter rain and hail storms in northwestern plains and occasional heavy snowfall in hilly regions are caused by these disturbances. These are generally followed by cold waves in whole of northern plains.
(b) Easterly Jet
During summer, due to the apparent shift of the sun in northern hemisphere, the reversal in upper air circulation takes place. The westerly stream is replaced by easterly jet stream which owes its origin to the heating of the Tibetan plateau. This leads to the development of an easterly cold jet stream centered around 15°N latitude and blowing over peninsular India. This helps in the sudden onset of monsoons.