Chennai lies on the thermal equator, and thus sees little variation in seasonal temperature. Its proximity to the sea gives it a hot and humid climate for most of the year. The highest temperatures are experienced in late May and early June and usually vary between 38 °C (100.4 °F) and 42 °C (107.6 °F) though it sometimes nearly touches 45 °C (113 °F) for a few days. Average daily temperature in Chennai during January is around 24 °C (75 °F), though the temperature rarely falls below 18 °C (64 °F). The lowest temperature recorded is 15.8 °C (60.4 °F) and highest 47.1 °C (116.8 °F).

The average annual rainfall is about 1,300 mm (47.2 inches). The city gets most of its seasonal rainfall from the north-east monsoon winds, from Mid October to Mid December. Cyclones in the Bay of Bengal sometimes hit the city.

For administrative purposes Chennai is divided into five talukas. 1. Egmore-Nungambakam, 2. Fort Tondiarpet 3. Mambalam-Guindy 4. Mylapore-Triplicane 5. Perambur-Purasawalkkam.

The Chennai Metropolitan area consists of three districts namely Chennai city and the districts of Kanchipuram and Thiruvallur. The city area covers an area of 174 km² (67 mi²).The metropolitan area covers 1,177 km² (455 mi²). The city is divided on the basis of composition into four major parts: North, Central, South and West.

North Chennai is primarily an industrial area. Central Chennai is the commercial heart of the city and the downtown area. South Chennai and West Chennai, previously predominantly residential areas are fast turning into commercial areas, hosting a large number of IT and financial companies.

Contiguous satellite towns include Mahabalipuram to the south, Chengalpattu to the south west, Kanchipuram town, Sriperumpudur, Tiruvallur and Arakkonam to the west.