Turning Up the Science, Cooling Down the Playground: An Urban Heat Island Project

By Kristen Hurst

How Carver Elementary students used data, design thinking, and community voice to investigate extreme heat and reimagine their playground, by Kristen Hurst, an Elementary Prep Teacher/Science at Carver Elementary School in the San Diego Unified School District.

Investigating a Real-World Problem

Located in the Oak Park neighborhood of San Diego, Carver Elementary School serves a diverse community of learners and families. Our students attend school in a highly urbanized environment where access to green spaces and tree cover is limited. This reality is reflected on our own campus.

Our playground is approximately the size of two football fields, with nearly two-thirds

covered in asphalt and blacktop and the remaining third consisting of dirt fields. We have only one small tree tucked away in a corner of the playground, providing very little shade for students during recess and lunch. As temperatures rise throughout the year, many areas of our campus become uncomfortably hot, directly impacting our students' daily experiences.

What began as conversations about the heat quickly evolved into discussions about fairness. Students recognized that many schools in more affluent neighborhoods have natural grass fields, mature shade trees, and cooler outdoor learning spaces. They questioned why their school environment looked so different and whether all students should have access to safe, comfortable, and inviting places to learn and play.

These observations inspired our Urban Heat Island Project, which began with a simple but important question: How can we make our playground cooler? Students noticed that certain parts of the playground became extremely hot during the day, especially areas covered in asphalt and blacktop. They wondered why some places on campus felt much hotter than others and what could be done to improve them. Through scientific investigation, data collection, and community engagement, students explored the causes and impacts of urban heat islands while developing solutions that could create meaningful change on our campus. By connecting science with issues of environmental justice and equity, students discovered they could use their voices and data to advocate for improvements benefiting both current and future generations of Carver students.

Collecting Data Like Scientists

Through this project, students investigated the effects of urban heat islands by collecting and analyzing temperature data from different areas around our school. Using thermal imaging cameras, infrared thermometers, clipboards, and data sheets, students measured the temperatures of blacktop, playground equipment, dirt fields, shaded spaces, and the few locations on campus with vegetation. They quickly discovered that surfaces such as asphalt absorb and retain heat from the sun, resulting in significantly higher surface temperatures than in areas with shade or plant cover.

One of the most memorable moments occurred during our beginning of data collection early in the school year, which was held as a Family Friday event. Families joined students in our auditorium for a brief introduction to urban heat islands before heading outside to participate in the investigation.

Students took on the role of scientists, leading family members to various locations around campus, explaining the project's purpose, demonstrating how to use the equipment, and recording data.

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The reactions from both students and families were immediate. Many were shocked when blacktop temperatures climbed above 150°F while shaded areas measured significantly cooler. One parent remarked, "I knew it was hot out here, but I had no idea it was this hot." Another commented, "Now I understand why my child always complains about the playground being too hot during recess." Students were equally surprised. One exclaimed, "This is hotter than the air temperature!" while another observed, "No wonder nobody wants to sit over here."

The investigation was built upon the San Diego Unified School District's 5th-grade STEAM unit, Cooler Communities. This unit was developed in partnership with the SoCal Heat Hub at UC San Diego. While the district lessons provided a strong foundation and catalyst for action, our students wanted to focus specifically on their own campus and playground. We expanded the unit by conducting a campus-wide heat-mapping investigation in which students identified study locations, developed research questions, collected multiple rounds of temperature data, and analyzed patterns over time.

Before collecting data, students developed models and predictions about which surfaces would be hottest and coolest and justified their thinking using evidence. During data collection, students worked collaboratively in teams with clearly defined roles, including equipment managers, data recorders, and site investigators.

After gathering data, students organized their findings using tables, graphs, and color-coded campus maps to visualize temperature differences across the playground. These visual representations helped students identify patterns and support claims with evidence.

Understanding the Impact of Urban Heat Islands

As young scientists and climate champions, students used evidence from their investigations to better understand how human activity affects Earth's systems and land surface temperatures. By comparing temperatures across campus, students identified the hottest zones on the playground and explored how vegetation and shade can help cool communities.

Students learned that trees, plants, and shade structures are important not only for comfort but also for enhancing environmental health, reducing heat-related impacts, improving stormwater management, and increasing climate resilience in urban environments. The project helped students understand that urban heat islands are not merely a scientific phenomenon; they are also a community issue affecting people's health, safety, and quality of life.

Designing Solutions for a Cooler Playground

Using the Design Thinking Process, students generated ideas for a redesigned playground featuring more trees, shaded areas, and greener spaces. They designed and built models of their ideal playgrounds to visually represent solutions for reducing heat on campus. Students expressed their learning through artwork, presentations, research displays, and call-to-action letters advocating for change in our community.

The Design Thinking process played a central role in helping students move from understanding the problem to proposing meaningful solutions. Rather than simply learning about urban heat islands, students became designers, researchers, and advocates working to improve their own school environment.

Empathy: Students reflected on their own experiences during recess and lunch, sharing stories about avoiding certain parts of the playground because they were too hot. Through classroom discussions, observations, and temperature investigations, they connected scientific data to their daily lives while exploring issues of fairness and equity.

Problem Identification: After analyzing temperature data, students identified the core challenge: large portions of the playground become excessively hot due to a lack of shade, vegetation, and heat-reducing infrastructure. Students supported their conclusions with heat maps, graphs, thermal images, and field observations.

Ideation: Students researched solutions used by cities, schools, and communities around the world. Topics included rain gardens, permeable pavement, rooftop gardens, increased tree canopy, shade structures, cool pavement coatings, and the benefits of natural grass. Students were especially interested in learning how reflective surfaces can reduce heat absorption and why artificial turf often reaches significantly higher temperatures than natural grass, while creating additional environmental concerns.

Prototype: Students transformed their ideas into tangible designs. Working individually and in teams, they sketched playground redesigns and built three-dimensional models of their ideal schoolyard. Their prototypes incorporated additional trees, outdoor classrooms, rain gardens, grass play spaces, permeable pathways, and shaded gathering areas.

Testing and Feedback: Students shared their prototypes with classmates, educators, community partners, and district leaders during a culminating showcase event. Visitors reviewed the designs, asked questions, and provided feedback about feasibility, effectiveness, and community impact. Students used this feedback to refine their thinking and strengthen their proposals.

By following the Design Thinking process, students moved beyond identifying a problem and became active participants in creating solutions. The experience demonstrated that young people can use science, data, empathy, and creativity to address real challenges in their communities and advocate for positive change.

Student Voice Inspiring Real Change

The culmination of the project was an Environmental Justice Showcase where students shared their research, data, heat maps, playground models, and proposed solutions with families, educators, community partners, environmental advocates, and district leaders.

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The showcase was part of a broader outreach effort designed to ensure that student voices reached decision-makers and community stakeholders. Students played an active role in planning and promoting the event.

Working collaboratively, they helped design a professional invitation in Canva, which was distributed to district leaders and school administrators. Invitations were also shared with community partners involved in local environmental initiatives and restoration efforts, including organizations and advocates engaged in Chollas Creek restoration and dechannelization work.

Students also wanted to learn from the people attending the showcase. Together, they developed a visitor survey to gather feedback and encourage meaningful dialogue. Survey questions asked attendees about their first impressions of our playground, what they already knew about urban heat islands, permeable pavement, and rain gardens, and whether they would be interested in receiving project updates or partnering with students in future efforts. Students viewed the survey as an opportunity to gather community perspectives and educate visitors about environmental justice issues affecting our campus. The showcase transformed students from learners into experts.

Visitors moved from station to station, asking questions and providing feedback while students confidently explained their research process, defended their design choices, and shared evidence supporting their recommendations. Many district leaders and community partners expressed appreciation for the depth of student thinking, the quality of their research, and the thoughtful solutions they proposed.

Because of the students' research, outreach efforts, and advocacy, we are already seeing growing support and conversations about making meaningful changes to our playground. More importantly, students learned that their voices matter and that they can use science, data, and civic engagement to bring positive change in their community.

Looking Toward the Future

This project helped students see that science is not just something learned from a textbook; it is a tool for understanding and improving the world around them. Through hands-on investigations, collaboration, design thinking, and community engagement, students learned that they have the power to use data, creativity, and their voices to inspire real change.

The Urban Heat Island Project began with a simple question about why our playground was so hot. It ended with students envisioning and advocating for a greener, cooler, and more equitable future for their school and community. In the process, they learned one of the most important lessons of all: meaningful change begins when people are willing to ask questions, gather evidence, and take action.