Making Urban Heat “Cool” Again



Written by Meredith Jennings, PhD, Postdoctoral Research Scientist, HARC and Jaime González, Houston Healthy Cities Programs Director, The Nature Conservancy, Texas

Our Next Big Community Challenge

It’s no secret that Houston is hot, but the latest trends show it’s getting hotter. Last August, Houston experienced seven days in a row topping 100 degrees, with all but two days that month meeting or exceeding the average maximum temperature for that day. If we pull back the lens even further, 2019 was the second warmest year on record globally, and the past five years have been the warmest five. With social distancing from the ongoing COVID-19 pandemic limiting how and where we stay cool, the impacts of urban heat are more important than ever.



Last summer, a report by the Union of Concerned Scientists made local headlines across the nation by calculating the number of dangerously hot days that are expected to increase in each city and county as a result of climate change. Looking at Houston specifically, if there’s no reduction in global greenhouse gas emissions, we can expect the average number of days with a heat index (or “feels like temperature”) above 105 degrees Fahrenheit to increase from 10 to 74 by 2065.

Increase in Heat and Its Impact on Quality of Life

This increase would, in turn, reduce the quality of life for all residents of the region and create especially dangerous conditions for those who engage in outdoor work and recreation, as well as communities striving to overcome historic obstacles around access to resources and opportunities. A future like this would also be highly detrimental to Houston’s wild residents, causing populations of certain plant and animal species to plummet. We’d see the impacts in the warming waters of our local bayous and in Galveston Bay, and we’d see fewer fledglings as a result of overheated bird eggs—in fact, we’re already seeing this trend in the beloved Northern Bobwhite, a favored game species.

While they can be motivating (and scary), we don’t need projections like these to understand how these chronically warmer summers have already negatively impacted our health and our environment. Within our region, many communities are already more vulnerable to urban heat because of a lack of air conditioning in homes—and for those who do have AC, few can afford to keep it running day in and day out to ensure a comfortable temperature.

When the August 2011 heat wave hit Houston, 30 out of 31 days exceeded 100 degrees and emergency department visits rose nearly 10 percent for adults 65 and older. Knock-on impacts like this underscore why it’s so vital that we increase energy efficiency in both our homes and our businesses. And we have solutions to lean on! Improving how your home is sealed and insulated through weatherization is one of the best ways to boost your home’s energy efficiency, making air conditioning more affordable and reducing the greenhouse gas emissions that contribute to climate change. But without weatherization or air conditioning as options to turn to, the survival of Houston’s wild populations of plants and animals will depend on more comprehensive and strategic city cooling.

Knowledge is Power: Mapping Heat Can Lead to City Cooling

Earlier reports, including HARC’s Cool Houston Plan (2004), have explored the potential to reshape our built environment to reduce urban heat by way of solutions like painting roofs white or adding green roofs, cool paving, and city-wide strategic tree planting. And there’s good news: more and more frequently, local planners and developers are incorporating heat mitigation strategies like these to improve both community comfort and stormwater management through smart urban design. A great example of this can be found in the reconstruction of Bagby Street in Midtown, which has gone on to receive national recognition.

Nature-first solutions to cool the city using shade trees, floodwater absorbing wetlands, and pocket prairies also provide a host of benefits including increasing air and water quality, adding greenspace in communities that need it most, and providing vital habitat for native species of birds and pollinators. Although it’s a true, stacked-benefit scenario, we still have to think carefully about how this is done. Beyond tree canopy targets, Houston will need a selection of tree species, shrubs, grasses, and wetland plants that are able to adapt to our highly dynamic climate, provide suitable habitat and food for our indigenous species, and—importantly—will not trigger a spike in allergies. These species will also need to be grown at a scale and sold at a price point that matches our challenges and needs. While it may seem daunting to implement, the work is worth the reward—and fortunately, we can look to other cities (like Dallas and Denver) as models for moving this needle forward Houston.

So, where do we begin? Earlier this year, Resilient Houston laid out a number of strategies to make Houston a more climate adaptive city, including “Action 16: Make Houston Neighborhoods Greener and Cooler to Combat Extreme Heat.” This action will begin with an initiative to measure and map urban heat in Houston and Harris County through a citizen science mapping campaign.

Formed as a collaboration between The Nature Conservancy of Texas, HARC, the City of Houston, and Harris County Public Health, the Houston Harris Heat Action Team (H3AT) is leading this endeavor to help us better understand on-the-ground distributions of heat at different times of the day throughout communities in Houston and the broader Harris County. This method of activating local volunteers to collect temperature data with sensors attached to cars or bicycles was developed by CAPA Strategies, Portland State University, and the Science Museum of Virginia and has been replicated in dozens of cities to date. Scheduled for early August, the H3AT heat mapping campaign and planning is already underway! For more information on the project and to find out how to become a volunteer, please visit h3at.org.

About our Guest Blogger

Jaime González, M.Ed.

Houston Healthy Cities Program Director, The Nature Conservancy in Texas

Jaime González serves as the Houston Healthy Cities Program Director for The Nature Conservancy in Texas. His work prioritizes building partnerships, designing and managing projects, and assisting communities and other organizations to help make Houston a more healthy, resilient, physically cooler, better-connected, and biologically diverse city. Mr. González also serves as the President and Co-founder of the Coastal Prairie Partnership, as the Secretary of the Board for the North American Association for Environmental Education, and as a member of Texas Parks and Wildlife Department’s Texas Wildlife Diversity Advisory Committee. He has worked for 22 years in the conservation and environmental education space in the Greater Houston region, including as the Community Conservation Director at the Katy Prairie Conservancy (2006-2018) and as Naturalist and Conservation Lead at the Houston Arboretum & Nature Center (1998-2005). Among other environmental, education and communication certifications, Mr. González earned a M.Ed. in Curriculum & Instruction-Science Education and a B.S. in Biology from the University of Houston.

And there’s good news: more and more frequently, local planners and developers are incorporating heat mitigation strategies like these to improve both community comfort and stormwater management through smart urban design.

Mr. Jaime González, The Nature Conservancy