1 Urban Form Effects on Personal Heat Exposure

Faculty Mentor: Alexandra G. Ponette-González (City & Metropolitan Planning, Natural History Museum of Utah, University of Utah)

Abstract

Salt Lake City summers are becoming increasingly hot and dry, with urban areas experiencing the greatest intensification of heat (Climate Central, 2025). However, urban heat is not uniformly experienced; temperatures can vary greatly even within a single city block due to differences in tree canopy and building form (Hu, et al., 2022). These factors influence how pedestrians experience heat by altering shade, airflow, and the amount of heat retained by surrounding surfaces. Understanding these spatial variations is key to designing cooler, more comfortable streetscapes, particularly as heat-related illnesses and mortality rise with climate change (Ebi et al., 2021).

This study explores variation in personal heat exposure at the pedestrian level across four walking routes in Salt Lake City that differ in urban form. Unlike many studies relying solely on satellite land surface temperature (Liu et al., 2024), this research employs low-cost wearable sensors to capture the microclimate directly experienced by pedestrians. This approach allows for a more human-centered view of heat stress in urban areas, revealing variations often missed in larger scale heat analyses.

To measure air temperature, we used the low-cost Kestrel D3FW monitor recording at a 2 second interval. GPS coordinates were also collected to match the temperature readings of the Kestrel using an Airbeam3 PM2.5 sensor. The four routes were selected to reflect a range of built environments and tree densities. Spatial data on tree locations and building types were collected through field observation and mapping prior to collecting temperature data to see how variations in greenery and building density might influence temperature recordings. We categorized the building type into three categories, low-rise (1-3 stories), mid-rise (4-9 stories) and high-rise (10+ stories). On Tuesday, Thursday, and Saturday from June 17th to July 12th, we conducted a walking survey from 4:00 PM to 6:00 PM. This time was selected due to the typical rush hour traffic patterns and high afternoon ambient temperatures. For the purpose of this study, we focused on two days, July 1^st (hotter) and July 5^th (cooler), to assess how urban form influences personal heat exposure under contrasting weather conditions.

Results show that Route 2 (West Downtown) consistently recorded the highest and the greatest variation in temperatures, coinciding with a higher concentration of mid- and high-rise buildings and fewer trees. This suggests that taller, denser buildings may intensify heat exposure by reducing shade, increasing surface heat absorption, and limiting air circulation. Although Route 4 had the highest number of trees, it was not the coolest, indicating that vegetation alone may not fully counteract the heat effects of densely built environments. Overall, both vegetation and building height play a role in shaping urban heat, with Route 2 standing out as a high-priority area for increasing tree canopy to reduce pedestrian-level heat.

These findings suggest that both tree cover and building form shape pedestrian heat exposure, with vertical density potentially exerting a stronger warming effect than tree canopy alone. To mitigate this problem, urban design strategies should prioritize not only expanding tree cover but also adjusting building forms, promoting air corridors through the West Downtown area or incorporating green infrastructure to enhance cooling.

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