We hate to rain on your parade, but that’s exactly what is forecast for Anzac Day.

Heavy rain could drench the dawn service and the Anzac Day march through Melbourne’s streets on Wednesday, when thousands will gather to pay tribute to those who served and died in battle.

Bureau of Meteorology senior forecaster Richard Carlyon said 20-40 millimetres of rain was expected from Tuesday afternoon to Wednesday morning as a low pressure system near south-western Victoria tracked along the south coast.

"It’s looking quite wintry and wet over the next few days," Mr Carlyon said.

"There will be some reasonably significant rain and unfortunately it looks like it’s still going to be here on Anzac morning.

"I think around dawn it will still be quite wet with some fairly cool conditions."

The mercury is expected to dip to a cool 10 degrees at 6am on Wednesday, and rise to a maximum of 17 degrees in the day in the city.

But despite the dismal forecast, organisers of the Anzac Day commemorations in Melbourne said the dawn service and march would go ahead as planned — rain, hail or shine.

The dawn service will begin at 6am at The Shrine of Remembrance, with those attending asked to arrive by 5.45am. Then from 9am, more than 12,000 war veterans and their descendants are expected to participate in the Anzac Day Commemoration March.

For the first time, due to Swanston Street tram works, the focus will be on St Kilda Road, with the assembly area outside the National Gallery of Victoria International.

Mr Carlyon said moderate rainfall was also expected about the central and Gippsland coasts on Anzac Day with cool and moderate to fresh south-westerly winds.

The showers will fall as snow in alpine areas, before the rain eases in the afternoon.

Mr Carlyon said intermittent rain was expected in Melbourne for the Anzac Day blockbuster between Collingwood and Essendon at the MCG in the afternoon.

"There might be breaks in the rainfall through the afternoon, so it will be a little better from that point of view but still not really ideal conditions," he said.

"It’s a deep low pressure system that’s currently south of Portland and it is expected to move north- eastwards to be on the Gippsland coast on Anzac Day morning. That will just bring in all the rain and strong winds up from the south-west during Tuesday afternoon and Wednesday morning."

The MCG said the initial release of public reserved seats for the Anzac Day match sold quickly and were all allocated by March 7.

A limited number of tickets went sale at noon today as a result of unused club, AFL and corporate allocations.

• Just after 2pm today, thunderstorms and hail swept across Melbourne and the temperature dropped nearly three degrees in the space of an hour.

Mr Carlyon said the storms swept through so quickly that only 1.2 millimetres of rain fell in the city. The highest rainfall recorded was eight millimetres at Scoresby.

"Most locations we saw the winds gust up to about 60-75 km/h as the storms moved through," Mr Carlyon said.

"There is still a chance of some hail and thunder about but the worst might be over this afternoon."

Residents at Northcote, Berwick and Glen Waverley reported large hailstones.