It even gets to the point where it's hard for me to breathe…I just look for shade. - Study participant
People experiencing unsheltered homelessness in Salt Lake City face hours of dangerous daytime heat and hot nights that offer little relief, according to a University of Utah study. Researchers also found that tree shade helps people feel measurably cooler, making it a critical resource for those without access to shelter.
The findings are featured in Unsheltered Homelessness and Extreme Urban Heat in Salt Lake County, Utah, a report released on Oct. 5 that brings together three U-led studies examining extreme heat and unsheltered homelessness. The research combines real-time heat measurements with interviews with people experiencing homelessness and local business staff to identify heat risks, barriers to finding refuge and ways to provide better protection.
"When it's hot, we go inside. If it's cold, we go inside. If the air quality is poor, we have places to find refuge. If you don't have access to secure housing, that's a huge problem," said Jeff Rose, associate professor in the Department of Parks, Recreation, & Tourism at the University of Utah, lead author of the study and coauthor of the report.
Hot days, sleepless nights
It'll break you down emotionally and mentally. -Study participant
Published Sept. 1, 2026, in the Journal of Urban Health, the heat-measurement study is one of the first to track personal, real-time heat exposure of people experiencing unsheltered homelessness. Researchers followed eight participants in Salt Lake City from July 29 through Aug. 3, 2024. Participants carried GPS-enabled cellphones and portable heat sensors as they went about their daily lives, allowing researchers to measure their heat exposure and compare it with surrounding tree canopy.
Researchers collected nearly 10,000 heat-index observations to track the intensity and length of participants' heat exposure during the day and overnight. During the daytime, participants were exposed to moderate risk (91 °F) nearly 20% of their daytime hours. High (103 °F) and very high/extreme risk conditions (115 °F) were less common, less than 4% of the time, but they did occur.
Nighttime offered little relief. Participants spent an average of 69% of nighttime hours above the "hot night" threshold (68 °F), when sleep tends to be disrupted, and 16% in "very hot night" (77 °F) conditions.
"Salt Lake City is getting hotter," Rose said. "One of the things that really came out from our study is that people experiencing homelessness have a lot of hot nights where they're not finding that low temperature at night that allows their bodies to re-regulate."
Extreme heat can lead to heat exhaustion, heat stroke and other potentially life-threatening conditions. For people experiencing unsheltered homelessness, heat may exacerbate existing medical conditions, disabilities and mental health challenges.
"This isn't just about fairness and justice. It's also about survivability, particularly when we're dealing with extreme environmental conditions," Rose said.
Trees are public health infrastructure
Cops chase us off with 30-second countdowns. -Study participant
The researchers found that time under tree canopy was associated with heat-index reductions of about 1.7 to 3.2 degrees Fahrenheit between noon and 6 p.m. The cooling effect increased with time spent beneath the canopy before tapering off after 15 minutes.
While businesses and other indoor spaces may offer temporary refuge, access isn't guaranteed. For people without shelter, public trees can provide an alternative place to escape direct sunlight.
"Trees are often viewed as ecological amenities, but they're also a form of public health infrastructure, especially for those with no shelter from rising urban heat," said Rose.
But barriers still exist. Participants sometimes spent less than 10 to 15 minutes under tree canopy due to access issues, limiting the shade's cooling benefits. The authors emphasize that trees can't replace secure housing or indoor cooling during extreme heat.
"Code Red" and other policies
The October report draws on preliminary findings from two additional U-led studies. Interviews with 24 people experiencing unsheltered homelessness revealed that access to shade, drinking water, bathrooms and places to rest can be as important as the temperature. Participants described heat-related illness, disrupted sleep and emotional strain, as well as displacement from public spaces. Many relied on community and mutual-aid networks for support.
A third study, based on interviews with 30 business managers and staff, found that businesses often serve as informal cooling refuges, but access and practices vary. These spaces can't reliably substitute for coordinated public cooling resources.
The report calls for a statewide "Code Red" policy that would activate emergency protections during dangerous heat, including extended access to public cooling spaces such as libraries and senior centers, and outreach to those at greatest risk.
Putting shade where it's needed most
There are no drinking fountains in this park anymore. - Study participant
The researchers recommend prioritizing tree planting and other cooling resources in hotter, heavily paved and underserved neighborhoods, including parks, riparian corridors, public plazas and other shared spaces.
They also stress that people experiencing homelessness should be included in decisions about tree planting, park management and access to public shade. Policies that displace people from shaded areas can undermine the benefits of investments in urban green spaces.
"Shade is the bare minimum. We really should be providing other cooling mechanisms, but we have these natural solutions that really help everybody," Rose said.
Protecting people from extreme heat requires immediate resources and longer-term solutions, including accessible cooling spaces, drinking water, shade and secure housing.
"We're ultimately talking about humans who are living through this," Rose said. "These are folks with hopes and dreams and ambitions and setbacks, just like the rest of us."
By measuring heat exposure and identifying barriers people face in finding relief, the research provides evidence that the authors hope will guide urban forestry, public-space planning and heat-protection policies as temperatures rise in U.S. cities.
This work was funded by the Wilkes Center for Climate Science and Policy at the University of Utah and by the National Science Foundation (grant No. 2323996).
