Rescuers are struggling to reach affected villages in eastern Uttar Pradesh but are being hampered by rains expected to continue another two days.
Relief Commissioner K.K. Sinha says 13 people died in Mirzapur district "when the roof of their mud houses collapsed."
Jaunpur's additional magistrate P.K. Upadhaya said Monday that many of the 18 killed in his district were in bed and "died in sleep."
More than 50 villages in Chandauli district are flooded, and rivers including the Ganga are above danger levels.
The northern Indian state is offering compensation of about $2,200 to victims' families.