Chennai lies on the coast and is quite close to the equator, and thus has a temperature that is almost constant and predictable throughout the year. Summers are very hot, with the monsoons helping to bring down mercury levels from the month of June. And it's the winter months, from December to February, though brief, that make for the perfect time to visit the city. There are so many places you can visit in Chennai, the temples, beaches, listen to concerts and of course relish the delicacies that are in tune with the seasons. Visit Chennai in winter when the weather is great and the sea breeze makes the land cooler. That way you can travel the city unflustered. 

Chennai‘s summers are very hot and humid, thanks to the proximity of the sea coast, which has led to the city fondly being called 'hot, hotter, hottest Chennai.' May is the month of ‘Agni Nakshatra’ or the firestar and the month is more sweltering and sweaty than the rest of the summer months. Schools are closed and most people head to the hill stations, or to the beaches and swimming pools in the evenings. But Chennai has the advantage of being under a sea breeze that turns the nights cool. Summer’s off season so you can expect good deals in accommodation.
Wear cool cottons, carry an umbrella and stay hydrated on water, tender coconuts and watermelons. Temperature averages between 28°C-40°C.

Southwest monsoon begins in June with little showers and less humid weather. As the southwest passes on, the northeast monsoon descends on Chennai by October with heavy rains and still heavier flooding. Chennai being at the coasts is also prone to floods and cyclonic storms during this period. The city is off season during monsoon, as low lying areas get inundated and roads turn slushy. But if you must travel, carry an umbrella and a raincoat. Average temperature would be 23°C-35°C.

Winter is pleasant here, with a cool breeze blowing in from the seacoast that helps rather considerably to remove the heat. Mornings are cooler and foggy, and the day time skies are clear. There might be occasional rain showers in December, so keep umbrellas and raincoats handy. Chennaites celebrate Winter with a music and dance festival in December and Pongal in January. Winter is the perfect and most idyllic time to go exploring the city and indulge in adventure sports. You find a number of birds migrating to Chennai's lakes during winter. Its a great time for birdwatchers and shutterbugs. Temperature ranges from 21°C-31°C.