Thunderstorms, drenching rain and even a tornado threat have helped deter racegoers from being track-side during Melbourne's spring racing carnival.

Crowd numbers fell even on days when the weather was kinder, with overall attendance for the four-day Flemington carnival down by 12,000 people.

More than 101,000 people headed to Flemington to watch Michelle Payne become the first female jockey to win the Melbourne Cup, 200 more than turned out in 2014.

The biggest declines came on Derby Day, which had early thunderstorms and heavy rain, and Oaks Day.

Racegoers on the traditional "ladies day" on Thursday copped a drenching in between bouts of sunshine as 34 millimetres of rain fell on Flemington.

Half of that fell in less than an hour and delayed racing for 20 minutes, although the funnel clouds that sparked a tornado warning for Melbourne bypassed the track.

CROWDS ON MAJOR RACE DAYS: (2015 v 2014)

* Caulfield Cup - 29,511 v 31,068

* Cox Plate (Moonee Valley) - 27,620 v 28,909

* Derby Day - 85,943 v 90,244

* Melbourne Cup Day - 101,015 v 100,794

* Oaks Day - 57,560 v 64,430

* Stakes Day - 68,711 v 70,051.

* Total Flemington - 313,229 v 325,519