In November 2025, a massive storm rolled across the lower Mekong River delta, dumping multiple inches of rain onto the wide, flat river plain that covers much of Cambodia.
The river rose and rose. The force of the water churned up mud from the river bottom. The muddy water flowed downstream and rushed into the many farming and fishing towns that line the Mekong's banks.
Forty-six-year-old Chhum Chhin experienced the flood firsthand. "The water was everywhere," she explained, standing in the shade of her home, which is elevated above potential floodwaters on 12-foot-tall concrete pillars in the central Cambodian village of Roka Thom.
Chhum has lived along the Mekong her whole life. Last year, she says, the water was higher than she had ever seen it. It washed away crops and left a thick layer of mud on everything in its path: vehicles, buildings and fields.
But the damage from the flood could have been much worse. When the water arrived, Chhum and all her neighbors were gone, along with their cows and chickens. There were no fatalities in her community. And when the water receded, residents went back to normal life almost immediately.
"The things we do here during a flood, they save lives," says Vy Sievmeng, the officer in charge for the disaster management committee in Cambodia's Tbong Khmum province, which is one of the most flood-prone areas in the country. "In the past, a lot of people died and a lot of livestock drowned when there were big floods," he says, but that no longer happens.
Cambodia's nascent success makes the country an outlier among its peers. Only about half the world's least developed and small island nations have functioning warning systems, according to a 2025 United Nations report, and the mortality rate from disasters is six times higher in countries without robust weather-warning systems.
As climate change causes more extreme and dangerous weather, from deadly heat waves to record-breaking hurricanes and flash floods, a growing consortium of U.N. agencies, governments and philanthropic groups is racing to make weather warnings available to everyone on the planet. And they are relying on local knowledge to make the warnings effective.
Cambodia's progress in protecting its residents offers lessons for other parts of the world about the profound lifesaving power of simple, low-tech weather warnings, particularly in places where there is already strong local commitment to protecting residents. It also highlights the many challenges of saving lives and livelihoods as the Earth heats up.
A deadly problem
Cambodia's annual floods carry nutrient-rich mud into the rice and vegetable fields that are the backbone of the country's food supply and economy. Seeds planted in that mud can grow incredibly quickly.
But the floods can also be deadly, routinely taking hundreds of lives. And flood risk is only growing in the region, as climate change makes Southeast Asian monsoons more extreme and less predictable. Periods of unseasonable drought are followed by torrential rain that leads to massive floods.
Just last year, widespread floods killed hundreds of people in five countries across Southeast Asia. In 2022, floods killed more than 1,000 people in Pakistan and displaced millions more.
One reason for the high death tolls in such disasters is a lack of basic weather-warning systems.
"Early warnings are not an abstraction," said U.N. Secretary-General António Guterres in a speech last year. "They give farmers the power to protect their crops and livestock, enable families to evacuate safely and protect entire communities from devastation."
The residents of wealthy countries generally get warnings before extreme weather arrives. In the United States, the National Weather Service issues official warnings that trigger alerts on radio, television and cellphones.
As a result, the U.S. has some of the lowest per capita fatality rates from weather in the world, despite widespread exposure to heat waves, hurricanes, wildfires and other extreme events, according to an annual climate risk analysis sponsored by the German government.
"We take that for granted in some places," says Jason Watkins of the World Meteorological Organization, which is part of the United Nations.
The quest to warn everyone, everywhere
In 2022, the U.N. set out to fix the global weather-warning problem. Guterres set a goal of extending severe-weather warnings to every person on Earth by 2027, with a $3.1 billion price tag.
The agency is not on track to meet that goal, and in 2024 Guterres noted that the least developed countries were still "lagging behind."
But money has been flowing nonetheless. So far, the U.N.'s Green Climate Fund has spent more than $2 billion on early warning systems around the world, and other major contributors — the Asian Development Bank and the World Bank — together have spent about $2.5 billion on such projects.
The United States has historically been a major contributor to the Green Climate Fund, but in January, the Trump administration said the U.S. would no longer participate in the fund. That will deprive the fund of billions of dollars in contributions but won't otherwise affect its operations, according to the United Nations. The U.S. has also officially pulled out of the landmark Paris climate agreement.
A portion of the international funding that has already been collected for early warning systems went to Cambodia, which is among the most flood-prone countries in the world. Between 2023 and 2025, U.N.-affiliated agencies spent $5.5 million upgrading the country's flood forecasts and warnings, and an additional $7.8 million will be spent in the coming years.
Representatives from Cambodia's disaster management, meteorology and hydrology agencies declined to be interviewed, saying they were too busy managing crises related to the ongoing conflict between Cambodia and neighboring Thailand. Still, at a 2021 event launching the U.N.'s work in Cambodia, Cambodian officials welcomed international investment in the country's flood-warning systems. "Quick action is needed to manage flood risks, so international cooperation is very important," said Soim Monichoth, who helps lead Cambodia's Ministry of Water Resources and Meteorology, according to a World Meteorological Organization account of the event.
"There certainly has been progress over the last few years," says the World Meteorological Organization's Watkins, who leads the United Nations' work in Cambodia. Residents who used to get little or no warning about floods now get flood forecasts up to five days in advance, thanks to upgrades to weather-forecasting computer models and the satellite data that they rely on, he explains.
And with U.N. support, local leaders in three communities reworked evacuation plans to better protect the most vulnerable people, including those who live in low-lying areas and those who are elderly or have small children. That effort is supposed to expand across the country in the next three to four years.
The U.N.-backed program also tapped into long-held community knowledge. The program funded local meetings with residents where community members talked about which areas were most flood-prone, since longtime residents often have the most granular and useful information about how water moves across the landscape.
"We know which areas have the most severe flooding," says Chan Chomroeun of the Pursat Provincial Committee for Disaster Management in central Cambodia, which oversees an extremely flood-prone pilot area near the country's massive Tonle Sap lake.
Watkins says that local expertise is crucial. "People are very much in tune with the land — they rely on the land for their livelihoods," explains Watkins. He sees the U.N. funding as a support system for the work that local people are already doing, as opposed to a top-down solution.
The power of a voicemail
One of the areas that received U.N. support is the fishing village of Prek Touch, on the banks of the Mekong River north of the capital. Long wooden boats line the water. Women clean the day's catch as men repair their nets.
Floods are a normal part of life in the late summer and fall months, when monsoon rains cause the river to rise repeatedly. The houses are on tall stilts, and usually the living quarters stay dry even when the water is at its highest. Most families have lived there for multiple generations.
For decades, floods killed people in the village each year. Children were particularly likely to drown, says 49-year-old Kly Phally, who has four children. "We tried to keep them from playing near the water during the floods," she explains. But residents didn't always know when the water would rise or how high it would get. And they had nowhere to evacuate to, so most families just stayed in their homes and waited out the water.
That began to change about 10 years ago. Between 2013 and 2015, the local government opened an evacuation shelter — a compound with space for livestock as well as people — on higher ground nearby, and it launched a new weather-warning system with the help of the European nonprofit People in Need. Residents with cellphones could sign up for weather alerts, which came as voicemails and text messages on the popular communication app Telegram.
But not everyone has a cellphone. As part of the U.N. initiative in the last few years, local leaders were encouraged to find ways to warn vulnerable residents — including elderly people, those with small children and others who might need help evacuating — when a flood is coming.
The solution they came up with was simple. When a flood is coming, local officials in Prek Touch and another village that received U.N. support hook up their phones to their car speakers and drive through town broadcasting the warnings at high volume, so people who don't have cellphones can hear the details of the warning firsthand.
The alerts now end with this request: "If you receive this message, please inform your friends, colleagues, all family members and those in need in your community."
A life-or-death test
Years of efforts were put to the test in 2025, when some of the worst flooding in memory swept across Cambodia.
As torrential rains fell across the region in early November, a cellphone alert went out, warning residents in Prek Touch that a flood would occur the next day, and telling them to evacuate.
"They used the loudspeaker to tell everyone," says 82-year-old Ker Sman, who has lived in the village his whole life and says he is its oldest resident. Although he has a cellphone, he says he did not receive a flood alert on it.
After he heard the loudspeaker warning, Ker was unsure what to do. He put his belongings in his home and considered sheltering there, as he had in the past, although he was worried that his home might not survive if the water rose too high. When he saw that everyone else was evacuating, he decided to do the same. A neighbor gave him and his wife a ride to the shelter.
Every household did the same, residents say. "When we heard the alert, we put everything in the house, locked the door and then took the children and the cattle to the shelter," remembers Kly, the mother of four. "We were safe there."
It ended up being the right decision. "The water flowed very fast," remembers Kly, pointing across the road at the 20-foot concrete pillars holding up her neighbor's home. About 15 feet off the ground is a smudged line of mud: the high-water mark. No one would stand a chance in such a torrent.
The entire village camped out at the local evacuation shelter for a few days, along with their cows and chickens. After the water receded, life went back to normal within a couple of weeks, Kly says. There was one fatality, according to residents: a young child whose family lives on a boat and so wasn't able to evacuate.
Saving lives, losing livelihoods
Cambodia's successes are still relatively small scale, says the World Meteorological Organization's Watkins. In late 2025, Cambodia's government officially endorsed U.N. efforts to expand weather warnings across the country and give residents even more time to evacuate before floodwaters reach them.
But saving lives is just the first step, residents say. In interviews with nearly two dozen people in two of the most flood-prone provinces in the country, the same theme emerged over and over: Cambodians are surviving floods only to return to ruined fields.
"The water washed away all my seeds," said 58-year-old Chhay Sophal, as he raked sticks off his empty plot in December. He doesn't own very much land. Losing one harvest means he has nothing to sell for months, he explained. More than half of Cambodians are directly involved in agriculture, according to a survey conducted last year by the United Nations.
It's a reminder that floods can be economically devastating, even if they are no longer deadly.
"What would help? We need levees, dams and retention ponds, so we can control the water better," says Vy, the disaster official in Tbong Khmum province, which includes the area where Chhay farms. "If we could collect the water during floods, we could use it to irrigate the fields when the weather is dry."
Better weather forecasts could also help. In many wealthy countries, the government provides seasonal weather forecasts, which can help farmers make decisions about which seeds to plant and where and when to plant them. Such forecasts require sophisticated data analysis.
"In the future, we'd like to develop some tools that can provide seasonal information," says Watkins. "This is the reality for many people."
Mom Sophon contributed to this story.
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