Melbourne Cup racegoers back at the track

Victoria's social event of the year had touches of everything as crowds flocked back to the track for the Melbourne Cup.

Thunderstorms, heavy rain and hail failed to dampen the spirits of an estimated 70,000 racegoers who converged on Flemington, with attendance dwarfing the 10,000 at last year's Cup and none in 2020.

Temperatures dropped to 10C, making Tuesday the coldest Cup day in decades.

Sporting bold fascinators and ties while clutching umbrellas, punters gathered in brightly-coloured frocks and tailored suits to watch the race that stops the nation.

Supermodel Adut Akech and racing heiress Kate Waterhouse led the star arrivals inside the exclusive Birdcage enclosure.

Punter Marty Johnson said it was a relief to have some freedom after an extended lockdown during the COVID-19 pandemic.

"It's great to see everyone about and to engage with the world again," Mr Johnson said.

"This is an iconic event and probably one of the best days of the year so it feels awesome to be out and about again."

Mitch Ogden travelled from Queensland for the annual event.

"This is my first time in Melbourne, I've been here for about a week - I'm originally from Brisbane so it's great to see it down on the ground instead of on the screen for once and even with the weather, everyone is still out having a good time so I'm really happy to be here," he said.

Before dawn an unidentified person allegedly broke into the racecourse to protest the "toxic" racing industry, pouring an oil-like substance on the track.

Victoria Police said it was investigating the incident, with climate change activist group Extinction Rebellion Victoria applauding the stunt as Racing Victoria scrambled to repair the damage.

"Melbourne Criminal Investigation Unit detectives are investigating after unknown offenders have broken into a racing facility in Flemington and poured an unknown substance over a portion of the track about 6am this morning," Victoria Police said in a statement.

There was almost as much action outside the Flemington gates as animal rights activists turned heads with bold signs calling for an end to the "archaic" sport.

The Coalition for the Protection of Racehorses urged people to say "Nup to the Cup", saying 139 racehorses died on Australian tracks in the past racing year.

Racegoers continued the festivities as a hailstorm swept through later in the day.

One shirtless punter appeared to be in high spirits as he let loose with a makeshift slip and slide on the field as the hail rained down.

Many looked worse for wear as the event came to an end but a strong police presence ensured there was little to no anti-social behaviour.

This year's Melbourne Cup Carnival partnered with local charity GIVIT to support flood-impacted people and communities throughout Australia.