Flood warnings were posted along France's Garonne, Adour and Midouze rivers early Monday in the wake of Friday's heavy rain and gusts that packed winds said in one spot to have been the worst in 20 years.
That was at Millau in Occitania where 142 kilometers per hour (88 miles per hour) was recorded by meteorologists.
The third victim was found dead Sunday afternoon in a submerged car east of Dax. The motorist in his 40s had gone missing on Friday.
On Saturday the body of a pensioner was found near Espien in Lot-et-Garonne Department. He had been washed away by flood waters while trying to empty his letter box.
On Friday a 70-year-old motorist died in the French Basque country when his car hit a tree that had fallen across a local road.
Emergency services dealing with the weekend disruption extracted the occupants of some 20 vehicles from flood roads, reported the news agency AFP late Sunday.
As a precaution, in Saint Martin-de-Seignaux, residents of a retirement home had been transferred to another facility, it reported.
The weekend's tempest was the third to grip France since November.
Two weeks ago at least six people lost their lives in southern France. Storm winds and torrential rain in southeast France in early November also claimed six lives.