The warnings came in fast, and Rajendra Dawadi did not wait.

The headteacher at Tribhuvan Trishuli Secondary School in Nuwakot, which has 1,600 pupils, said he halted classes and ordered children to higher ground after getting four warnings from different people within minutes, including one from Betrawati, a town directly upstream.

“I decided I shouldn’t delay any more,” he told the BBC. “Even if the flood was not coming, it was just a matter of a single day’s classes.”

Dawadi said that during the school evacuation he saw a hostel building about 100 metres from the river being engulfed by the torrent of flood water.

“If we had made the decision 10 minutes later, all of us, including the students and me, would not be able to speak to you today,” he said.

One student said Dawadi’s decision saved their lives with moments to spare.

Yunisha, 16, told reporters: “I, along with my friends, survived by just 10 seconds.”

She said the children ran up a muddy path to escape as water and debris inundated the town.

“Within no time, the bazaar was swept away in front of my eyes,” she said.

She was reunited with her family three days later.

At least 69 schools have been destroyed or damaged by the floods, affecting nearly 19,000 children, according to the charity Save the Children.

In Dhading, one of the areas worst hit by the floods, a group of schoolchildren survived when they left their classroom for their lunch break.

Others in the area escaped when teachers told them to quickly evacuate classrooms just before the waters came crashing in.

The mother of one child told the Associated Press that teachers had warned students: “There is a flood and you should leave bags and tiffins. That’s how they managed to survive.”

More than 3,700 people have been rescued in Nepal so far.

The country said on Sunday that 2,502 people, including 592 foreigners, were out of contact. It reported an updated death toll of 781 people.

The disaster struck the Nepal-Tibet border region of the Himalayas on Wednesday morning. The US Geological Survey said a glacial collapse caused it, sending a wall of water and debris cascading downstream.

Nepal’s foreign minister has called for a global response to the climate crisis, saying the Nepali people had disproportionately become “major victims of climate change” despite having contributed a fraction of the planet’s fossil fuel emissions.

Read more from The Guardian.