Mumbai/IBNS: At least four people have died, of which three were electrocuted in Pune as heavy rainfall, overnight and this morning, battered the three cities and other parts of Maharashtra Thursday.

A red alert has been declared for Mumbai and Palghar.

The observatory in Mumbai's Santacruz has recorded over 1,500 mm of rain so far this month, making it the second wettest July in the city's history. The city received under 1,771 mm last July.

Four rivers in the state, including the Kundalika and Amba, are flowing above the danger mark and threaten to destroy villages and settlements along their banks. In addition, the Mithi River, which is adjacent to Mumbai's Chhatrapati Shivaji Airport, flows just a metre below that mark.

Rains have affected flight ops at the airport with IndiGo and SpiceJet warning passengers of "periodic delays in flight schedules, while Air India offered full refunds for cancelled flights.

Videos and photographs shared online showed extensive flooding in parts of the city.

High waves have been reported along Juhu Beach, prompting police and local officials to warn people to stay away from the coastline.

Like Mumbai, Pune also faces a red alert till Friday morning.

The Army and NDRF have been called in to help disaster response teams, with authorities reporting severe flooding in areas like Ekta Nagri and Vitthal Nagar and in housing societies in Kalyaninagar.