In the east African cities of Nairobi and Dar es Salaam, hundreds of thousands of slumdwellers find themselves increasingly battling flooding brought on by extreme rainfall linked to climate change.
One problem is a lack of forecasts that are simple and useful enough that they could effectively warn them of coming trouble.
"You have people living in places where they are not receiving (useful) weather information," said Gea Mikic, a researcher with Resurgence, a British-based social enterprise working to cut climate risk.
In cities where more than half of the population lives in urban slums, that's a big gap.
But her organisation is now working to equip 800,000 slumdwellers in the two cities with simple forecasts - possibly sent through text message - that could help them prepare for and avoid the worst impacts of flooding.
Crucially, "we are connecting them to the people who are producing this information" to make sure they get what's most useful, in the most useful form, she said Sunday at a conference on the sidelines of the U.N. climate negotiations.
Delegates from around the world this week are entering the final stretch at U.N. talks in Poland to agree rules on how to implement the Paris Agreement to curb climate change.
But help for the world's estimated one billion people who live in slums and are battling worsening weather challenges - an eighth of the world's population - remains uncertain.
Slumdwellers, or those living in "informal settlements", often struggle to access money or other assistance to battle climate change impacts and grow cleanly, as most of that help goes to national governments rather than cities, much less informal parts of cities.
Cities around the world are taking action on their own. Many have organised to cut carbon emissions and curb the effects of climate change through a range of networks that link cities and share expertise, from C40, a group of cities which is seeking to slow global warming, to 100 Resilient Cities, a network helping cities around the world face up modern-day pressures.
But informal areas are rarely a priority, particularly with cash that might help moving largely through national governments, said Sheela Patel, who founded the non-profit SDI, formerly known as Slum Dwellers International, the largest global movement of slumdwellers in the world.
"When I look at climate change, I see several real challenges. The urban poor are not seen by national governments as worthy of national attention," she said. "The rural poor are the good poor."
Slumdwellers are so marginalised they are often not even counted by authorities - and as a result are not part of urban plans, she said.
"Most cities are in denial of the informality in their city," she said.
With the world's climate increasingly unpredictable and freak weather like heavy rain more frequent in many areas of the world, however, that means extra efforts are needed to keep slum areas afloat.
SDI, for instance, has focused recently on trying to better understand how many people are affected by flooding in urban slums, and what might best help them.
In India, Bijal Bramhmbatt, who heads the Mahila Housing SEWA Trust, said that because slums often lack proper drainage, even regular rain lead to low-level flooding that damages homes.
The non-profit works with women to tackle the problem by connecting them with tech entrepreneurs who can help find low-cost fixes to help, she said.
In the Brazilian Amazon, Ana Carolina de Lima, of the University of Para, said she had seen significantly worsening flooding in many towns near the mouth of the Amazon, because they are receiving more rain as a result of climate change, and because many sit at or below sea level.
The problems they face are in part man-made, said the environmental anthropologist.
Urban planners often protect main streets by channeling excess water away with makeshift embankments, some made of trash.
Much of that can end up in slums.
"If it rains ... you have all this water in your backyard, below your house that stagnates there," she said. "And that causes a whole lot of health problems."
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