Thousands more have been forced to leave their homes, and Prime Minister Shahbaz Sharif has appealed for international help.
The large volumes of water destroyed the dams at a major control system on the Swat River, causing the river to overflow its banks in Charsadda and Nowshera districts.
More than 33 million people, equivalent to one in seven Pakistanis, have been affected by the monsoon rains. Almost one million homes have been seriously damaged or destroyed.