Now, as the floodwaters appear to recede, a massive relief effort is under way with participation by celebrities such as Anil Srinivasan, a classical pianist, and unsung people who just want to help.
"This is something of a megadestruction movie," said Srinivasan, who lives in the city's suburb of Nungambakkam. "It's bizarre and unreal."
Since October, flooding killed at least 272 people in the region, according to the National Disaster Response Force. About 28,000 people had to be rescued. The flooding knocked out government services, left people stranded and made small boats a commonplace sight in city streets.
The National Crisis Management Committee recently said about 90% of the city has power and buses are running again. Telephone services are not yet fully functional. Train service is spotty but should be back to normal Monday.
The recent weather has been especially grueling lately.
In early December, 397 millimeters (nearly 16 inches) of rain fell during a two-day period in Chennai. In November, 1,196 millimeters (47 inches) of rain fell, according to CNN Weather, more than three times the average monthly rainfall of 353 mm (14 inches).
The flooding brought out a helping spirit among residents of Chennai, once known as Madras and India's fifth-largest city. The restoration of Internet service proved crucial for relief efforts.
"The value of Wi-Fi access cannot be underestimated," said Sharanya Manivanan of Chennai. "Phone lines were down for days, but those with Internet access were able to make things happen."
She said people started collecting food and other supplies without knowing how it would be distributed. Others had braved the waters to reach the drop-off points.
"It's been the people all the way, the average Chennai citizen," Manivanan said.
Local relief efforts
Tech workers created a crowdsourcing site called www.chennairains.org so people can find sources of food and shelter using their smartphones or computers.
Volunteers such as Balaji Mohan prepared three meals a day for people with no access to clean food or water. Volunteers have cooked, packed and distributed meals to about 7,000 people.
Srinivasan set up a relief center called "Find and Provide" in Gopalapuram in central Chennai where supplies coming in from Bangalore and Mumbai are stored. Private groups have set up hundreds of other similar centers, he said.
Lack of phone and Internet service left relatives outside of India worried about loved ones.
Bala Sundaram of Atlanta said he didn't have any information about her parents for nearly 72 hours.
"My parents' neighbor informed my sister in Bangalore that they were doing OK and relieved us of the tension," Sundaram said. "The people network has been so strong which has helped the city more than anything else."
Maya Harita, who lives in a suburb outside Atlanta, took to Facebook to get help for her aging parents in Chennai. They had to move upstairs to escape rising water.
"The entire house is wrecked and all their gadgets, equipment, beds, couch, belongings have been destroyed," Harita said. "All that is left is lots of mud, bugs and snakes."
Many people took advantage of the Safety Check feature on Facebook, which allowed them to let family members outside the country know they are safe.
Full air service expected to resume
The Indian military rescued thousands of people stranded without power, electricity or water, Srinivasa said. He said private groups such as the Madras Boat Club and the Tamil Nadu Sailing Association have also helped, as well as local fisherman.
The return of full air service to Chennai should make it easier for donations from outside nations to arrive.
Most airlines were expected to resume normal service by Sunday at Chennai International Airport, a huge gateway to the south of India and one of the country's busiest airports.
Some air service had been canceled flights because of water on the tarmac. Several airlines, including TruJet, SpiceJet, IndiGo and Air India, had diverted flights to Arakkonam, a nearby military airfield 55 miles west of Chennai, according to the State Government of India.
"Drinking water is a megaproblem, then cooked food of any kind, followed by milk and baby food," Srinivasan said. "Other supplies like blankets and sanitary napkins are also needed."