Heavy rain and thunderstorms have drenched much of Victoria ahead of the Melbourne Cup and more is on the way, causing significant transport delays.
Bureau of Meteorology senior forecaster Michael Efron said 17.4mm of rain fell in Melbourne in the four hours up to 11am on Tuesday, and up to 10 mm was still on the way.
Melbourne Cup goers are urged to pack an umbrella and maybe some not-so-fashionable gumboots as the city braces for a deluge, with temperatures to top at a humid 20C.
The heavy rain has also seen the Flemington track downgraded to a heavy eight, with races two and three pushed back.
That's good news for late arrivals who might find it difficult to get to the racecourse due the weather playing havoc with Melbourne's public transport system.
Flooding near Flemington is causing train delays of up to 20 minutes and a number of inner-city tram services have been stopped because of storm damage.
Interstate visitors planning to jet out later in the day might also face delays, with Air Services Australia tweeting that Tuesday morning's poor weather could cause problems.
"We can expect showers during the race but it's unlikely it will be as heavy as this morning," Mr Efron told AAP.
It might also be a good idea to pack a warm coat, with southerly winds forecast to bring cold temperatures in the late afternoon, as punters leave the course.
"People heading home from Flemington are likely to have a pretty cold trip," the forecaster said.
It could be particularly cold for flamboyant British billionaire Marwan Koukash who has vowed to accept the trophy in a G-string if his horse Magic Circle wins.
"That's the lace that's going to stop the nation," he told AAP at Monday's Cup Parade.
A severe weather warning is in place for Melbourne and eastern parts of the state, as a slow moving low pressure trough brings heavy rain and thunderstorms.
Those storms could lead to flash flooding in some parts.
Sunbury, as of 11am, reported rainfall of 43mm, and 21mm of rain had fallen at Melbourne Airport.
