The dead -- seven of them children under the age of 5 -- were all reported to be in the southeastern town of Batman. Soldiers were attempting to rescue the stranded, and the mayor of Batman closed schools for two days, the state-owned Anatolia news agency said. Dozens were reported missing.
On Wednesday, at least 22 people were confirmed dead in the flooding. Fourteen people died when floods overwhelmed a minibus in Cinar on the road from the region's largest city Diyarbakir as it traveled to a wedding in the neighboring province of Mardin.
Another three people were killed in floods in Diyarbakir's Bismil district after hours of heavy rain overnight swept away many vehicles. Six people were still missing there.
Helicopters and boats supported rescue efforts in Cinar and Bismil, bringing to safety 300 people stranded in their homes.
Authorities sent a 25-strong search and rescue team to help with relief efforts in the southeastern province of Sirnak bordering Iraq, where four people died, including two infants.
Some houses were also damaged in the floods. Among the dead in Sirnak was a 70-year killed by falling debris from a house.
Heavy rainfall and flooding were also affecting other parts of the country, closing down roads and highways along the coast and forcing some to evacuate their homes in Istanbul.