Toronto’s Urban Heat Island: Exploring the Relationship Between Land Use and Surface Temperature
by Mushtaq Hussain © 2010

Increasingly warm temperatures in urban areas are becoming a major concern for planning and public health officials. The built environment with its different land uses is considered to be contributing to rising temperatures and more frequent extreme heat events. In the context of Toronto’s urban heat island, this paper explores the association between land use and surface temperature using 2009 land use data and surface temperature derived from a 2008 Landsat Thematic Mapper (TM) thermal image. Zonal statistics revealed that mean temperatures were high for commercial and resource/industrial land uses (29.1oC) and low for parks/recreation (25.1oC) and water bodies (23.1oC). The differences between temperatures for these land uses were statistically significant. In addition, a correlation analysis revealed that surface temperature tends to increase as polygon area increases for commercial and resource/industrial land (r = 0.405 and 0.259 respectively), and decreases as polygon area increases for parks/recreation land and water bodies (r = -0.264 and -0.323 respectively). In an alternate approach based on kernel density, it was found that temperature tends to increase as the concentration of commercial and resource/industrial land uses increases, and to decrease with concentration of parks/recreation and water bodies. Such concentrations of homogenous land use associated with high surface temperature were identified in north and south Etobicoke, northwest North York, and northeast Scarborough. To mitigate hot surface temperatures, it is recommended that municipal planners and decision-makers review regulations and formulate policies that are specific to “hot” land uses, in particular commercial and resource/industrial.