Heavy rains have lashed stretches of the country near the Afghan border since Thursday.
Fourteen children and three women were killed in "rain-related incidents" in K-P province, local relief official Taimur Ali said.
The National Disaster Management Authority (NDMA) confirmed those deaths, adding that three more people had died in Balochistan.
Six including five minors killed, as rain lashes K-P
In the worst single incident, five children were killed when the roof of their home collapsed in Dargai town.
Rain also damaged another 51 houses and snowfall blocked several roads in Azad Jammu and Kashmir, officials said.
More harsh weather is expected in the coming days.
Many poorly built homes across the country -- particularly in rural areas -- are at risk of collapse during the annual spring rains.
Torrential downpours, avalanches, flooding and harsh winter weather killed more than 130 people across Pakistan and Afghanistan in January.
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