It's the race that stops a nation with the fashion to match, but you won't be race-day ready on Tuesday without an umbrella and poncho.

Wet weather protection could prove your best racing tip, with moderate to heavy rain forecast overnight until 10am or 11am on Melbourne Cup day.

The good news is falls will ease into the afternoon for the all-important race.

“We are looking at a quite a wet start to the day on Tuesday. It's not completely dry for the race, but still not as bad as what we're expecting during the morning,” Bureau of Meteorology senior forecaster Michael Efron said.

“For people heading to the race, take a brolly and poncho.”

A top of 20 degrees is forecast on Tuesday, with a minimum of 17.

It will be cloudy and humid with a 90 per cent chance of showers, most likely in the morning and early afternoon and the chance of thunderstorms.

A severe weather warning is likely across the state's central and eastern areas.

There is also potential for some isolated rainfalls of 30 to 50mm.

It won't come close to the wettest Melbourne Cup day, though, which was in 1942 when 46.5mm of rain fell.

On the record-breaking front, it also won't be the hottest or coldest.

The hottest Melbourne Cup was 35.1 degrees in 1902 while the coldest was in 1913 when racegoers shivered in 11 degrees.

In pre-Cup festivities, showers are expected on Monday for the Cup parade in Melbourne's CBD, amid humid conditions.

“We do have a few showers around at moment and they'll continue throughout the afternoon,” Mr Efron said.

“We're not expecting constant rain, but do take your brolly and a poncho if you're heading out to the parade today.

“As we head into the late afternoon and evening there's a risk of a storm as well.”

A top of 26 is expected on Monday with showers and a possible storm.

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