Central Madhya Pradesh state has suffered the highest death toll with at least 17 people killed in flood-related incidents, officials said.
And in eastern Bihar state, at least 15,000 people have been evacuated from their homes after a “flood-like situation” in a dozen districts.
Floods are common in India during the monsoon season between June and September.
But excessive rains this year have caused the Ganges river and its tributaries to rise above the danger level in about 20 districts in the states of Madhya Pradesh, Bihar and Uttar Pradesh.
At least 13 people have died in Bihar and Uttar Pradesh states because of drowning, electrocution or injuries sustained after house collapses.
In Bihar, where at least six rivers are flowing above the danger mark, thousands of people have taken shelter in more than 80 relief camps, reports say.
People have taken shelter on the roofs of their submerged huts, and houses along the banks of the river are inundated.
“We are facing a lot of problems, everything has been submerged in river. There is no arrangement of food, drinking water or boats. We don’t know what to do,” a resident in Patna city told Reuters news agency.
In the neighbouring state of Uttar Pradesh, the Ganges river has been flowing above the danger mark, and people living in low lying areas have been moving to higher ground.
“Water has been gushing in the area for the last three days. All the land has been inundated with flood water. All the crops have been damaged. Water has started entering our houses,” said a villager, Shyam.
