United Nations chief Antonio Guterres on Friday began a two-day visit to flood-hit Pakistan that officials hope will bolster global support for a humanitarian crisis affecting millions.

A third of the country is under water – an area the size of the UK – after record rain brought on by what Guterres has described as a “monsoon on steroids”.

Pakistani officials say it will cost at least $10 billion to rebuild and repair the damaged infrastructure – an impossible sum for the heavily indebted nation – but the priority for now is food and shelter for millions of homeless.

“Everything is drowned, everything washed away,” said Ayaz Ali, who was suffering from a fever as he reluctantly took his place on a naval boat to rescue villagers from flooded rural communities in southern Sindh province on Thursday.

In a tweet en route to Pakistan, Guterres said he wanted “to be with the people in times of need, mobilizing international support and bringing global focus to the catastrophic effects of climate change.”

Pakistan receives heavy – often destructive – rains during its annual monsoon season, which are vital to agriculture and water supplies.

But a downpour as intense as this year has not been seen in decades, and Pakistani officials blame climate change, which is increasing the frequency and intensity of extreme weather around the world.

Pakistan is responsible for less than one percent of global greenhouse gas emissions, but ranks eighth on a list compiled by the NGO Germanwatch of countries considered most vulnerable to extreme weather conditions caused by climate change.

A flood relief plan drawn up last month by the Pakistani government and the United Nations called for $160 million in immediate international funding, and aid is already arriving.

On Thursday, a US Air Force C-17 – the first American military plane to land in Pakistan in years – brought much-needed tents and tarps as temporary shelter.

While Washington is a key supplier of military hardware to Islamabad, conflicting interests have left ties uneven in neighboring Afghanistan — particularly since the Taliban returned to power there last August.

The weather bureau says Pakistan has received five times its normal rainfall in 2022 — Padidan, a small town in Sindh, has been soaked by more than 1.8 meters (70 inches) since the monsoon began in June.

The heavy rains had two effects – flash flooding in rivers in the mountainous north that washed away roads, bridges and buildings in minutes, and a slow accumulation of water in the southern plains that has inundated hundreds of thousands of square kilometers ( miles) of land.

In Balochistan’s Jaffarabad district, villagers fled their homes on makeshift rafts made of upturned wooden “charpoy” beds.

Thousands of temporary campsites have mushroomed on arid strips of land to the south and west – often roads and railroad tracks are the only rise in a landscape of water.

With people and livestock crammed together, the camps are ripe for outbreaks of disease, with many reported cases of mosquito-borne dengue and scabies.

The floods have claimed the lives of nearly 1,400 people, according to the latest report from the National Disaster Management Authority.

Almost 7,000km of roads were damaged, some 246 bridges were washed away and more than 1.7 million homes and businesses were destroyed.