The mayor of Cannes, David Lisnard, announced in an interview with BFM TV that he would seek explanations from higher authorities. The Cannes authorities received a warning of the approaching storm just an hour before it hit.
Heavy rains are also said to have caused flooding at popular swimming pools and leisure centres in Antibes.
The French meteorological agency said another storm could hit Cannes in the afternoon. A yellow warning has been issued for southern France.
Flash floods in Cannes as central and eastern Europe battles worst flooding in two decades
The flash floods in Cannes came as Central and Eastern Europe was struggling with the effects of flooding caused by the low-lying Boris Genoa in this part of the Old Continent. Floods caused by heavy rains have killed 17 people in Poland, Romania, the Czech Republic and Austria. This is the worst flooding in Europe in two decades.