CLICK HERE for an update on the floods as death toll rises to four
One of the missing was a 77-year-old man.
Near Muy, in the Car area, a woman was also missing after a lifeboat capsized with three crew members and three other people aboard. While five of them reached safety she could not be found.
Two other people were rushed to hospital as storms hit the area overnight.
The two districts affected, Alpes-Maritimes and Var, were placed on “red alert” warnings by the meteorological office and official warnings were also issued about high waves off the coast.
A total of 1,600 members of the emergency services were mobilised to deal with the emergency.
Numerous roads were cut off and rail traffic was halted from the Cote d'Azur to the Italian border until at least Sunday.
Flights from Nice international airport were suspended during the day and due to resume late Saturday.
In Nice itself, alert sirens sounded to urge people to stay indoors. Most residents complied and the streets were almost deserted by late afternoon on Saturday.
Four thousand homes were left without electricity due to the bad weather and flooding.
In several towns, including Hyeres and Frejus, hundreds of residents were evacuated as a preventative measure. Shelter was provided in municipal buildings.
A 39-year-old woman was seriously injured after being carried along by a wave, according to firefighters.
A 78-year-old man was also hospitalised with hypothermia after being trapped by a tree trunk brought down by a landslide.
The French authorities warned late Saturday that with more heavy rain on the way and rivers in the area already overflowing their banks that the flooding will continue to worsen”.
They urged local residents to stay indoors, be careful near water courses and not to use their vehicles unless strictly necessary.
Other regions of southern France, including Gard and Haute-Loire, were put on orange weather warnings.