In Mathare – a collection of informal settlements northeast of Nairobi, Kenya, housing more than 500,000 residents – heat is reshaping daily existence. Most buildings in Mathare are constructed from materials like corrugated metal, which trap and magnify heat, forcing residents outside during the day. But that, said Michelle Koyaro, Program Associate at Slum Dwellers International (SDI) Kenya, offers little respite. Improper waste disposal and pollution have eroded air quality, which, along with elevated temperatures during the day, induces headaches and fatigue. “When heat rises, it reduces productivity and increases stress,” Koyaro said. “Alongside the health aspect, it’s really affecting people’s livelihoods.” Street vendors have had to adjust their hours to vend during the evenings, leading to loss of income, and lack of cool storage within homes has put a strain on families’ food budgets.

A Global Challenge with Local Impacts

Heat is almost always expressed numerically. But in cities, heat is more than a number; it’s a felt experience – something that, as Koyaro heard from community members in Mathare, fundamentally changes how people live. Heat can vary significantly from neighborhood to neighborhood, even block to block. Studies have found that temperatures can vary by 7 degrees Celsius or more within cities – different enough that some parts of a city may be considered under a heat wave while others are not.

And what people require to cope with extreme urban heat – which is only intensifying as climate change accelerates – can vary widely across cities, too. Resilient buildings and natural infrastructure can help to shield communities from the impacts of heat. But communities like Mathare, that lack these resources, are disproportionately exposed. Differences in infrastructure often align with socioeconomic demographics within communities, so underserved neighborhoods experience more extreme heat. Understanding these variations can inform how cities design and enact responsive policies, from which neighborhoods to prioritize for additional cooling infrastructure (like planting trees for shade and designing passive buildings) to where rapid-response aid should be targeted during extreme heat events.

Although more cities are beginning to recognize the need to take action against extreme heat, they face two key barriers: 1) a lack of hyperlocal data on heat and 2) a general lack of awareness and participation in urban heat mitigation efforts from local stakeholders.

To help cities tackle these barriers, WRI Ross Center for Sustainable Cities and the Africa Research and Impact Network (ARIN) with support from data.org – an organization focused on accelerating the potential of data and artificial intelligence against the world’s greatest challenges – engaged residents and community-facing organizations like SDI Kenya in participatory heat mapping efforts in Nairobi. By encouraging local residents and leaders to share intimate knowledge about local heat challenges, cities can build the kind of nuanced, responsive databases they need to develop effective, community-based heat mitigation efforts.

Uniting Diverse Stakeholders To Further Understanding and Action

In Nairobi, WRI Ross Center and ARIN assessed the potential to overcome a specific challenge faced by many African cities: limited deployment of weather sensors to monitor temperature variation. Technical staff recognized that the first step would be to identify and work with a broad range of local stakeholders who could inform, and eventually support, a community-based sensor deployment campaign. Measuring heat exposure across communities, Koyaro said, “needs to be a participatory process. Community members need to be actively involved in collecting data, and for sensors, they need to be brought into managing them.”

Throughout 2024, WRI Ross Center and ARIN conducted an extensive stakeholder identification exercise, spanning community-based outreach, research, interviews and assessments of interested participants. The stakeholder identification phase, which began in July 2024, culminated in October 2024 with an in-depth workshop that gathered all interested stakeholders to determine roles, assess next steps and identify potential areas for initial sensor deployment campaigns.

During the workshop, stakeholders’ diverse perspectives offered invaluable insights on how to move forward. Participants made clear that different areas of the city will require vastly different approaches for successful sensor deployment campaigns. Through a collective discussion about temperature variations across the city using land surface temperature maps provided by WRI Ross Center’s Urban Data and Tools team, participants validated that informal settlements in the central and eastern parts of the city, such as Mathare, Mukuru and Kibera, are already facing more extreme heat risks compared to other areas of Nairobi.

For areas most vulnerable to extreme heat and experiencing the worst of its’ impacts, participants noted that engaging local youth and women – who tend to spend the most time within communities and have the strongest connections and awareness of local needs – will be critical to effective measurement and mitigation campaigns.

In areas like the central business district, there will be a greater need to engage with the Nairobi City County government, local businesses and community volunteers. Participants in the workshop agreed that the sensor deployment and community outreach efforts must focus on places where already-vulnerable people live or frequent, like informal settlements, schools, hospitals and road networks.

Participants like Koyaro, who have deep experience with community engagement, felt the potential of coming together as a coalition. “As organizations, we have a lot of initiatives, but we haven’t consolidated the information we all hold so that it can be used as a comprehensive advocacy tool,” she said. By aligning on a baseline understanding of current conditions and a path forward for enhancing data collection, stakeholders can work together more effectively – and collaborate on how to expand their lens. “Beyond mapping only where people live, we also need to consider where people work. Is there a way we could map these journeys so we could understand what other local organizations we might need to engage?” Koyaro said.

To Koyaro, it’s essential that any sensor deployment campaigns not just task community members with managing the sensors – they must ensure residents are empowered through the process. “We can’t just gather data from communities and not share it back with them – otherwise, they won’t have knowledge. We find that a lot of people still don’t understand the links between climate and health. We need to share the data from this effort back with communities in usable format[s] and ensure that what the data is showing resonates with them. And we need to make sure that the insights are shared throughout the community in a way they can engage with every day.” Koyaro cites murals that SDI Kenya has developed in communities as an effective way to foreground both the impacts of climate change and the potential of community-based resilience efforts.

Building Momentum To Tackle Heat Locally and Globally

Supported by data.org, WRI Ross Center and ARIN’s engagement with local organizations and residents to inform the creation of robust, localized heat data tracks with efforts to elevate heat as a priority across multiple levels of government in Kenya, said Elizabeth Wangeci Chege, Energy Efficiency and Cooling Specialist at Sustainable Energy for All (SE4All). “Within ministries and the private sector and building sector, there is a huge lack of awareness around [the] urban heat island effect that we’ve been working to counter,” she said.

SE4All supports Kenya’s clean energy transition through various initiatives, including its National Cooling Action Plan. But, Chege says, “conditions across the counties are very different. We have microclimates and different economic conditions within and across counties.” As SE4All supports eight counties across Kenya to develop heat action plans, the organization notes a need for the kind of localized heat data that WRI Ross Center, ARIN and data.org aim to produce. Neighborhood-scale data on extreme urban heat must be combined with data on everything from hospitalization rates (to understand health impacts) to tree cover (to identify priority areas for investment in nature-based solutions), so both national and county governments can proactively build financial and programmatic responses. “When we say we need to reconsider how we meet the needs in our cities, we need data to inform the path forward,” Chege said.

Following the workshop, WRI Ross Center and ARIN will support stakeholders in Nairobi to design heat measurement and awareness campaigns informed by the insights generated from this workshop. But the work doesn’t stop there. The ultimate aim is to provide tangible guidance on community-engaged data collection for Nairobi and then create a roadmap for peer cities conducting similar, local heat data collection efforts.

The outcomes from this first phase of stakeholder engagement and action planning demonstrated the power of bringing diverse perspectives and skills from across a city to the same table to tackle the collective – yet hyperlocal – challenge of extreme urban heat. As rising temperatures continue to impact people’s health and daily lives, it’s vital that cities work directly with their residents to understand the risks they face to target and scale meaningful solutions.

WRI Ross Center for Sustainable Cities’ data.org-supported work in Nairobi is part of a broader portfolio of projects addressing and mitigating extreme urban heat through data collection and analysis, passive cooling and smart infrastructure, and policy engagement. Learn more.

Eillie Anzilotti is Communications Lead for UrbanShift at WRI Ross Center for Sustainable Cities.

Maddie Palmieri is Communications Associate for Urban Development at WRI Ross Center for Sustainable Cities.

Ruth Engel is Environmental Health and Extreme Heat Data Scientist for the Urban Data & Tools team at WRI Ross Center for Sustainable Cities.