At least hundreds, and possibly thousands, of people have visited the dam wall in recent days to see the spectacle. The spillway started flowing last week, and about 40,000 megalitres of water are now passing through the gates each day.

The dam, near Albury, is now 97 per cent full, up from 50.5 per cent at the same time last year. Its peak last year was 50.6 per cent.

"We've been releasing from Hume now for the last two weeks in order to maintain some airspace in the dam," said Andrew Reynolds, of the Murray Darling Basin Authority. "[It is] to keep the level of the dam down a little bit, so that when we get rainfall we can reduce the size of the flood or the flow that comes out of the dam."

"Initially, we released through the power station and the valves, so we had enough capacity through those. Once that was exceeded ... we put some releases through the spillway gates."

The spillway is expected to keep flowing, at least in the near term, given the healthy inflows into the huge dam and the further rain forecast.

Water storages across Victoria are filling rapidly following steady rain over recent days and a wet winter. Laanecoorie Reservoir, about 40 kilometres west of Bendigo, has undergone a rapid transformation.

"It filled on Saturday and went from about 50 per cent of capacity to full in about 15 hours," said Andrew Shields, of rural water company Goulburn-Murray Water (GMW).

"It's a good response given the wet nature of the catchment and the good rainfall on Thursday night and Friday."

Inflows into seven GMW storages in the past two months alone were greater than for 2014-15 and 2015-16 combined.

Another storage, Lake Eildon, has climbed to 60 per cent full after receiving 345.8 gigalitres of inflows in August, almost three times the volume in August last year.

The soggy conditions and forecasts for more rain mean a number of flood warnings are in place. A moderate flood warning is in place for the Loddon and Glenelg rivers, while there are minor flood warnings for the Avoca and Kiewa rivers.

Initial minor flood warnings have been issued for the Campaspe River, Werribee River at Ballan and Lerderderg River at O'Briens Crossing.

In central Victoria some roads have been covered with water, while some river flats were underwater on Tuesday.

Michael Efron, senior forecaster at the Bureau of Meteorology, said that from 9am on Monday to 4pm on Tuesday the highest rainfalls were recorded in the state's north-west, with 49 millimetres at Bullengarook, 48 at Blackwood and 44 at Navarre.

"We've seen moderate to heavy rainfall across central and western districts throughout the last 24 to 36 hours, with some thunderstorm activity across the north-west of the state," he said.

"The heaviest falls have been around the ranges just to the east of Ballarat and also further north-west towards Charlton, around that part of the southern Mallee and eastern parts of the Wimmera."

The higher parts of the Glenelg River catchment, around the Grampians, could receive 20 to 50 millimetres overnight on Tuesday and into Wednesday. Melbourne is expected to receive five to 10 millimetres of rain on Wednesday, with most of it in the early morning.