MUMBAI, July 8 (Reuters) - Heavy rains flooded roads and railway lines on Monday in India's financial capital of Mumbai, disrupting flights and forcing the closure of schools and colleges, while overflowing rivers elsewhere affected more than 2 million people.

Just ahead of the morning rush hour, more than 300 mm (11.8 inches) of rain lashed the city of 12 million in the six hours until 7:00 a.m (0130 GMT), civic officials said in a statement.

With forecasts of more heavy showers and a high tide of 4.40 metres (14 ft) in the coastal city, school and colleges shut for the day as a precaution, the authorities added.

"There is heavy traffic on the roads and rail lines too have been affected," Eknath Shinde, the chief minister of Maharashtra, the western state whose capital is Mumbai, said on X, urging people to stay indoors unless necessary.

Commuters waded through knee-deep water that partially submerged vehicles in many areas, while traffic clogged the city's Eastern and Western Express highways.

Water on the tracks forced railway authorities to cancel some long-distance trains, they said, while television images showed some suburban passenger trains, a critical means of daily transport for millions, halted on inundated lines.

The rains, coupled with low visibility, prompted airport authorities to suspend runway operations for more than an hour from 2:22 a.m., airport sources said.

More than 300 flights were delayed and 36 cancelled, the website of tracking service Flightradar24 showed.

On X, India's biggest airline, low-cost carrier IndiGo , said its Mumbai flights were affected by the heavy rain, while another budget airline, SpiceJet, also warned of disruptions due to bad weather.

The heavy downpour came days after record-breaking showers in the capital, New Delhi, that caused the fatal collapse of an airport roof.

Torrential monsoon rains have also triggered floods and landslides in India's north and east, as well as in the neighbouring Himalayan nation of Nepal, where at least 11 people were killed.

More than 2 million people have been affected by rivers flooding in northeastern Assam, where the Kaziranga National Park, home to the rare one-horned rhinoceros, was inundated with six of the animals drowned, authorities said on Sunday.

State authorities said 66 people have died in floods and rain related incidents since May.

Flooding has also affected 31 villages in India's most populous state of Uttar Pradesh on the Nepal border, the state government said. (Reporting by Dhwani Pandya and Sudipto Ganguly in Mumbai, Tora Agarwala in Guwahati, Saurabh Sharma and Shivam Patel in New Delhi; Additional reporting by Swati Bhat; Editing by Clarence Fernandez)