The deluge hit the remote mountainous northern part of the Khyber Pakhtunkhwa region, with cloud bursts, flash floods, lightning strikes and landslides in the deadliest downpour of this year's monsoon season.
By Saturday, 307 were confirmed dead, with more people missing, according to the Provincial Disaster Management Authority.
Parts of neighbouring India and Nepal have also been hit hard by heavy rains, flooding and other rain-related incidents over the past week.
In Bajaur district, close to the Afghan border, Saeedullah was asleep in the yard of his home on Thursday night when he was woken by thunder.
He rushed to his house, where his family was sleeping, to find that the roof had collapsed.
Helped by neighbours, he dug through the debris and found the bodies of his wife and five children.
He said he suspected the house was hit by lightning, with parts of it on fire before the rain came down.
He said he buried his family on Friday, with the help of the community.
"There is destruction everywhere, piles of rubble," Saeedullah, 42, said.
Bilal Faizi, a spokesperson for the country's official rescue service, said that he expected the death toll to climb as more bodies are recovered from under the debris of homes.
Buner district, north of Pakistan's capital, Islamabad, was the worst-hit, with 184 confirmed killed so far.
Faizi said there was a cloud burst in Buner early on Friday, creating a torrent of water that swept down to the villages below.
"There was no time for anyone to react," Faizi said.
Zahid Hussain, 62, a resident of Beshonrai village in Buner, said that more than 60 people had lost their lives in his village and more than 20 were missing.
He said he told his family to flee when he noticed water rising quickly in a stream near his house that swept towards his front door.
One of his nephews got trapped and broke his leg as the waters rose. Hussain rescued him and took him to a hospital in Buner.
"The floodwater washed away our house in front of our eyes," Hussain told Reuters from the hospital.
"Within minutes, we were made homeless."
More than 30 homes in the village were swept away.
Ishaq Dar, the deputy prime minister and foreign minister, said that civilian and military teams were carrying out rescue and relief operations, while the prime minister had chaired an emergency meeting.
Provincial Chief Secretary Shahab Ali Shah said that local officials had been dispatched to the flooded areas to supervise relief operations and assess the damage.
He said medical camps were being set up for the flood victims, along with arrangements to provide food for families who lost their homes.
On Friday, a rescue helicopter crashed due to bad weather, killing the five crew members.
Zaheer Babar, Pakistan's chief meteorologist, said the country has seen an increase in the frequency and destructiveness of extreme weather events.
He said heavy rainfall in the mountains meant people in lower-lying areas were not aware of the strength of the downpour until it reached them as a flash flood.
Climate change was one factor, he said, but it was made worse by homes being built next to rivers and streams, while some waterways were constricted by construction activity and garbage dumping, making it harder for the rainfall to disperse.
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