National emergency services spokesman Michael Bernier said one person was missing in the wake of floods.
Thousands were being evacuated from the area, where officials said up to seven months’ worth of rain had fallen overnight.
Seven helicopters were scrambled to rescue people from the roofs of their homes, and rough weather was making operations difficult, the prefect of Aude, Alain Thirion, said.
The flash floods struck without warning. At least one victim was swept away by raging waters while sleeping, Thirion said.
Prime Minister Edouard Philippe, who will be heading to the disaster zone on Monday, said 350 firemen were helping the rescue effort and up to 350 more would be drafted in.
Water levels were expected to keep rising after more heavy rain. Schools were shut and residents told to stay at home.
Torrential rain is not uncommon in France at this time of year, but meteorologists have said exceptionally warm sea water along the Mediterranean coast may be intensifying the rains.