Australia's Grace Brown stormed to her first Olympic gold in the women's individual time-trial on Saturday raced over 32.4km of rain-slicked Paris streets.

The 32-year-old finished 1min 31sec ahead of Britain's Anna Henderson with world champion Chloe Dygert snatching third after a nasty fall, less than a second off silver.

US rider Dygert is also racing the road race and track events and took her final corners with particular care, rather than racing out of them.

Competing in her final season, Brown came fourth in the same event at the Tokyo Games.

A day after a prolonged downpour drenched the opening ceremony, lighter rain persisted, adding an edge of danger to the race through the streets of the French capital.

Czech rider Julia Kopecky finished down the rankings and admitted the course was frightening.

"I fell and it hurt I can tell you," the 19-year-old told AFP at the finish line.

"The crowd motivated me to finish fast," she said, adding the road race next Saturday was her target.

Ellen van Dyke of the Netherlands was expected to medal but came 11th, having broken an ankle in the Vuelta and returning to competition after having a baby last October.

Results from the Olympic women's individual time trial event on Saturday:

(Top 10 only)

1. Grace Brown (AUS) 39min 38sec, 2. Anna Henderson (GBR) at 1min 31sec, 3. Chloe Dygert (USA) 1min 32sec, 4. Juliette Labous (FRA) 1min 41sec, 5. Demi Vollering (NED) 1min 51sec, 6. Lotte Kopecky (BEL) 1min 56sec, 7. Kim Cadzow at 2min 08sec, 8. Elisa Longo Borghini (ITA) 2min 11sec, 9. Audrey Cordon-Ragot (FRA) 2min 13sec, 10 Christina Schweinberger (AUT) 2min 14sec