Fancy dress, grey clouds for Derby Day

Gusting winds and rain are dampening the start of Melbourne's glittering Derby Day but not punters' spirits.

Tens of thousands have arrived early for the start of the eight-day Melbourne Cup Carnival, with the traditional black and white dress code on display.

Following at a fashionably late pace were a long list of Australian and international celebrities, including Mad Men actor Rich Sommer and Beyonce's sister Solange Knowles.

Sommer challenged the celebrity behaviour model by actually watching and betting on the horse races from his place in the Schweppes marquee.

The actor - who plays Harry Crane in Mad Men - was planning to keep betting and punting, and head trackside later in the day.

"I've lost twice now," he said after Thunder Lady stormed home to win Race Two.

After a teasing burst of sunshine early in the morning, the weather closed in on Flemington Racecourse, threatening the hoped-for crowds of about 95,000.

As chilly winds menaced fascinators and intermittent rains challenged the resolve of the well-dressed punters staked out on the concourse, well-prepared revellers sheltered around umbrellas, champagne hampers and the odd Mercedes in the members' carpark.

Winds were no issue inside the lavish marquees of the Birdcage enclosure, where the gentle waft of air kisses was the only breeze to trouble celebrity guests, including Megan Gale, Jennifer Hawkins and musicians Benji and Joel Madden.

In the marquee of vitamin company Swisse, liver-cleansing shots were lined up at the bar alongside the bottles of vodka and champagne.

The Bachelor star Blake Garvey was among the guests - doing well on the social front for someone recently dubbed Australia's "most-hated" man.

Melbourne is facing a chilly afternoon with a top of 17 degrees as punters wait for the headline $1.5 million Victoria Derby, where trainer Gai Waterhouse's Hampton Court is favourite.