This Saturday is, in the words of Bureau of Meteorology senior forecaster Richard Carlyon, "the pick of the week".

The day promises a 24-degree maximum and with no showers forecast, the lawns of Flemington should stay dry. Only light northerly winds are predicted for the morning.

In short, the weather will be delightful come Derby Day. "It will a fine, mostly sunny day," Mr Carlyon said.

But if you were planning on wearing a dress with midriff cut-outs, that probably wouldn't be wise. Aside from it being too cold for bare skin, exposed midriffs are not allowed in the members' area, which also forbids denim, ripped clothing and parkas.

The forecast for Melbourne Cup day, however, is not as bright. Punters, racegoers and Cup-day barbecue hosts across the city shouldn't expect the sunshine to hold out.

While the bureau has not released an official Melbourne Cup forecast and will not do so until Tuesday evening, Mr Carlyon warned that a cold front is set to charge towards Melbourne on Sunday.

"It looks like a cool Melbourne Cup, we have (a top of) 17 degrees for Monday and it looks like something similar for Cup Day - the forecast will either come out as a shower or two or a possible shower," he said. "So a cool Cup day with a possible shower is our best forecast at the moment."

That cold front, from the Bass Strait, is expected to ensure a cold and wet start to the week, with showers and westerly winds predicted for Monday.

Last year, Derby Day was filled with chilly breezes and gentle rain with a maximum temperature of 25.9 degrees, and Cup day was cool but dry with a top of 17.9 degrees.

On Tuesday, Melburnians enjoyed a brighter than usual start to the day and relished the spring-like weather, with a forecast top of 24 degrees but a possible late shower.

It is a rare warm and sunny day for spring so far.

By this time last year, the city had enjoyed several days where with temperatures hovered above 30 degrees with no rain.

In September, the average temperature was 16.7 degrees, below the long-term average of 17.3. October, so far, is also below average.

- with Aimee Amiga