MELBURNIANS heading to the Cup Parade along Swanston St today should pack their umbrellas, with rain expected to soak the city throughout the day.

But Bureau of Meteorology senior forecaster Richard Carlyon said the weather gods might smile down on the city just long enough for the two-hour event.

“Probably the driest part of the day is likely to be in to be the late morning and early afternoon,” he told the Herald Sun.

“It’s best to be prepared but we are likely to see an easing of the showers through the morning.”

Thousands are expected to line the city thoroughfare for the parade, kicking off at noon at Bourke St before heading to Federation Square.

If some of the storm activity clears, the mercury could reach 26C today before a rainy evening ahead of Cup Day.

“There might be some thunderstorm activity later in the afternoon,” Mr Carlyon said.

“There could be enough rain to affect conditions tomorrow.”

The forecaster advised punters heading to Flemington tomorrow to prepare for a wet day, with up to 30mm of rain expected for Melbourne over the next 48 hours.

But the wild weather should clear for the main event.

“The risk of a thunderstorm should cease by race time,” Mr Carlyon said.

“The heaviest rain for Cup Day is looking like it will come through the morning.”

Melbourne is forecast to reach 20C tomorrow and 16C on Wednesday.

It will be 18C and partly cloudy on Oaks Day.

Temperatures are expected to rise back up into the low 20s by Friday, with the temperature to hit 21C with partly cloudy conditions on Saturday for Stakes Day.