Disaster relief officials said on Monday that at least 55 people were dead and 47 were missing in Sichuan province while in Chongqing municipality 24 were dead and 27 missing.
More than 450,000 people have been evacuated from the deadly storms, with 127,000 homes destroyed or damaged, 400 bridges collapsed and at least 720km of roads and thousands of hectares of farmland ruined.
"Among the dead and missing many are from Dazhou city. It is the heaviest rain in years and there are 30 dead and 30 missing there," Sichuan disaster relief bureau deputy director He Rongjun said.
"It has mainly been caused by landslides and mountain torrents, mud and rock flows," he added.
The cities of Nanchong and Bazhong have also been badly affected, although Dazhou was worst hit with 360 millimetres of rain since Thursday.
State television showed footage of flood water gushing down rivers in Sichuan.
The official Xinhua news agency said downtown areas of Dazhou were "isolated" as the rains caused cave-ins on urban roads and destroyed highways out of the city.
Parts of the city were under a metre of water.
Incessant rains have affected
millions since June
"Forty four districts and cities are affected with a population of more than six million," said He, who put initial estimates of economic losses at 1.3 billion yuan ($157 million).
Tang Wanli, an official from the Chongqing civil affairs bureau, said 24 people were dead and 27 were missing in his municipality, which neighbours Sichuan.
Tang said the rain was the heaviest recorded in certain districts in decades and that 1.2 million people were affected in one way or other.
According to meteorologists the worst hit area in the municipality, Kai district, has been drenched by 327.3 millimetres of rain since Thursday.
Relief in sight
Kai, scene of a gas leak that killed 243 people in December last year, was completely flooded. Power and telecommunications were cut and the bridge linking it with neighbouring Wanzhou district was destroyed.
Relief, however, appeared to be in sight.
Xinhua reported that the rain would stop by Monday afternoon, according to the meteorological bureau. And officials have launched rescue operations, although they were finding it difficult to get to more isolated regions.
Incessant heavy rains and floods have affected large swathes of China since June, killing hundreds of people and injuring thousands.