More than a month's worth of rain has fallen on Melbourne overnight, causing commuter chaos and hundreds of calls across the state to emergency services.
Melbourne recorded 54.6mm of rain in 24 hours to 9am, which is above the city's usual total for the entire month and the highest rainfall in March since 1929.
The wild weather brought down trees and caused damage to homes and flash flooding.
It prompted more than 300 calls for help across the state to the State Emergency Service.
State Response Controller Alistair Drayton said most callouts were for building damage. but expressed concern about the number of vehicle water rescues.
Mr Drayton said it only took 10mm to 15mm of water for smaller cars to float and people who drove in those conditions were making poor decisions.
Drivers are asked to exercise extreme caution and never drive through floodwater.
The wet conditions resulted in crashes and heavy delays.
On the public transport network, trains are resuming on the Hurstbridge line after earlier flooding closed it between Heidelberg and Clifton Hill.
There was also flooding on the Sandringham line between Sandringham and Elsternwick.
Burnley Station had significant flooding in its subway, with plumbers called to the site.
The downpour happened as ex-tropical cyclone Esther moved from northern Australia to the southeast, although it was not expected to make it as far as Melbourne.
"It is particularly unusual because usually these sorts of troughs weaken out before they make it this far south," Bureau of Meteorology duty forecaster Miriam Bradbury told AAP.
"They generally move east or die off, but this one has moved down to the southeast, so that's why we're getting tropical moisture and humidity."
A couple jumped off a pier in Port Melbourne to rescue their dog, which decided to go for a swim while on a walk about 10.15am despite the wild weather.
The woman returned to shore safely, and the dog survived, but a police officer had to jump in to help the man, before paramedics treated the pair.
The rain is forecast to ease in Melbourne in the afternoon, but the state's east will continue to receive heavy rain and possible thunderstorms.
A severe weather warning is in place for northeast Victoria.
Australian Associated Press