Thousands of fans braved downpours Sunday along the 87-mile (140-kilometre) cycling route, while Olympic riders battled to keep control as they flew across pools of rainwater.
In London's Greenwich district, wind and rain forced a brief delay at the equestrian events and pulled loose the roof of an enclosure housing tournament judges.
The archery competition was also blighted by downpours at Lord's cricket ground.
At the Olympic Park, Molly Wilson, from Michigan, wrapped her U.S. flag around her head in an attempt to fend off the rain.
"I will bring an umbrella next time," she said.