People were forced to trudge through knee-deep water in some streets in the Swat Valley. A newly constructed part of a dam in the Charsadda district collapsed, while crops were soaked in many areas. At least 10 people died near Peshawar when their homes collapsed.
Dozens of people were reported missing, including at least nine Chinese construction workers in the Kohistan area. Some 200 other Chinese workers were trapped amid the downpour, said Mian Iftikhar Hussain, the information minister for Khyber-Pakhtoonkhwa, the province that has been deluged.
He said it was the worst floods in the northwest since 1929 and estimated 400,000 people were stranded in various parts of the northwest.
"A rescue operation using helicopters cannot be conducted due to the bad weather, while there are only 48 rescue boats available for rescue," he said, noting weather forecasts predict more rain over the next 24 hours.
Monsoon season often leads to widespread flooding in Pakistan, imperiling residents in low-lying villages. The poorest residents are often the ones who live in the most flood-prone areas because they can't afford safer land.
The torrential rain this week is also a suspected factor in a plane crash in the Pakistani capital, Islamabad, that killed all 152 passengers on board Wednesday.