History:
The region around Chennai has served as an important administrative, military, and economic centre since the 1st century. It has been ruled by various South Indian dynasties, notably the Pallava, the Chera Dynasty, the Chola, the Pandya, and Vijaynagar. The town of Mylapore, now part of Chennai, was once a major Pallavan port. The Portuguese arrived in 1522 and built a port called São Tomé after the Christian apostle, St Thomas, who is believed to have preached in the area between 52 and 70 AD. In 1612, the Dutch established themselves near Pulicat, just north of the city.
On 22 August 1639, Francis Day of the British East India Company bought a small strip of land on the Coromandel Coast. The region was ruled by Damarla Venkatadri Nayakudu,, the Nayaka of Vandavasi. He granted the British permission to build a factory and warehouse for their trading enterprises. A year later, the British built Fort St George, which became the nucleus of the growing colonial city. Fort St. George housed the Tamil Nadu Assembly until the new Secretariat building was opened in 2010. In 1746, Fort St. George and Madras were captured by the French under General La Bourdonnais, the Governor of Mauritius, who plundered the town and its outlying villages. The British regained control in 1749 through the Treaty of Aix-la-Chapelle and fortified the town's fortress wall to withstand further attacks from the French and another looming threat, Hyder Ali, the Sultan of Mysore. By the late 18th century, the British had conquered most of the region around Tamil Nadu and the northern modern-day states of Andhra Pradesh and Karnataka, establishing the Madras Presidency with Madras as the capital. Under British rule, the city grew into a major urban centre and naval base.
With the advent of railways in India in the late 19th century, the thriving urban centre was connected to other important cities such as Bombay and Calcutta, promoting increased communication and trade with the hinterland.
Madras was the only Indian city to be attacked by the Central Powers during World War I, when an oil depot was shelled by the German light cruiser SMS Emden on 22 September 1914, as it raided shipping lanes in the Indian Ocean, causing disruption to shipping.

Geography:
Chennai is located at 13.04°N 80.17°E on the southeast coast of India and in the northeast corner of Tamil Nadu. It is located on a flat coastal plain known as the Eastern Coastal Plains. The city has an average elevation of 6 metres (20 ft), its highest point being 60 m (200 ft). Two rivers meander through Chennai, the Cooum River (or Koovam) in the central region and the Adyar River in the southern region. Both rivers are heavily polluted with effluents and trash from domestic and commercial sources. The Adyar, which is much less polluted than the Cooum, is de-silted and cleaned periodically by the state government. A protected estuary of the Adyar forms the natural habitat of several species of birds and animals. The Buckingham Canal, 4 km (2.5 mi) inland, travels parallel to the coast, linking the two rivers. The Otteri Nullah, an east-west stream runs through north Chennai and meets the Buckingham Canal at Basin Bridge.
Several lakes of varying size are located on the western fringes of the city. Red Hills, Sholavaram and Chembarambakkam Lake supply Chennai with potable water. Groundwater sources are mostly brackish.
The geology of Chennai comprises mostly clay, shale and sandstone. The city is classified into three regions based on geology, sandy areas, clayey areas and hard-rock areas. Sandy areas are found along the river banks and the coasts. Clayey regions cover most of the city. Hard rock areas are Guindy, Velachery, Adambakkam and a part of Saidapet. In sandy areas such as Tiruvanmiyur, Adyar, Kottivakkam, Santhome, George Town, Tondiarpet and the rest of coastal Chennai, rainwater run-off percolates very quickly. In clayey and hard rock areas, rainwater percolates slowly, but it is held by the soil for a longer time. The city's clayey areas include T. Nagar, West Mambalam, Anna Nagar, Perambur and Virugambakkam.

Weather:
The weather and climate of Chennai reflect the geographical location and relief of the Chennai city. Chennai lies near the thermal equator and the Sea that is why there is very less variation in seasonal temperature. For most parts of the year, the weather of Chennai is hot and humid. The hottest part of the year n Chennai and surrounding areas is late May and early June, with maximum temperatures around 38-42 °C. The coolest period is January, with minimum temperatures around 19-20 °C. Thus, for most parts of the year, the weather and climate of Chennai city remains moderate- neither too high nor too low.
Chennai city gets most of its rainfall from the northeast Monsoon winds (mid-September to mid-December). The average annual rainfall in the Chennai city is about 1,300 mm (51 inches). At times, the cyclonic disturbances in the Bay of Bengal affect the Chennai city.