The water quality of the Seine will be tested daily and it will also host the Ironman mixed relay on August 5, the Olympic marathon swim on August 8 and 9, and the Paralympic Ironman event starting on the 20th Eventing.
The Seine has been closed to swimming for more than 100 years due to high levels of pollution and risk of disease, but French authorities have invested heavily in making the river swimmable as part of the Olympic legacy.
Organizers say around €1.4bn (£1.2bn) has been spent on reconstruction projects to ensure the safety of the Seine.
Paris Mayor Anne Hidalgo recently swam in the river to highlight the cleanup efforts that have been carried out, and tests earlier this month showed the river was clean enough for swimming.
However, heavy rain in Paris on Friday and Saturday caused water quality to deteriorate.
Temperatures are expected to reach 35C on Tuesday, with thundershowers expected on Wednesday morning.
France currently lags behind EU average score, External To obtain high-quality bathing water conditions.
Between July 17 and 23, data showed the river, which cuts through the French capital, was suitable for swimming on six out of seven days.
As recently as June, E. coli levels were 10 times higher than acceptable levels set by sports federations.
