## 2 Materials and Methods  
### Study Area  
The study area falls toward the southern edge of Landsat Path/Row 38/31, starting at about 35 km north of Salt Lake City, Utah (Figure 1). The urban and exurban areas were classified as such based on the average percent developed imperviousness for each municipality. These values were derived from performing a mean Zonal Statistic on the NLCD 2011 Percent Imperviousness (2011 Edition, amended 2014) data (available at [33]) with the zones defined by the geospatial dataset \"Municipal Boundaries\" found on the UTAH Automated Geographic Reference Center (available at: [[https://gis.utah.gov/data/boundaries/citycountystate/](https://gis.utah.gov/data/boundaries/citycountystate/)]([https://gis.utah.gov/data/boundaries/citycountystate/](https://gis.utah.gov/data/boundaries/citycountystate/))). The results showed a natural break in percent impervious surface, with no municipalities having a mean percent impervious surface between 23% and 40%. This break was used to define the urban and exurban areas and is similar to the criteria used by [PERSON] et al. [34]. They saw that, for most of the largest biomes in the continental US except desert and xeric shrubland ecoregions, urban areas of 25% impervious surface area (ISA) or greater have a higher average LST than suburban and rural areas of less than 25% ISA. This classification resulted in the municipal boundaries of areas that had an average of 41%-51% imperviousness representing the urban area and included Clearfield, Ogden City, Roy City, South Ogden, Sunset, and Washington Terrace. The boundaries of areas that had an average of 5%-22% imperviousness represented the exurban areas and included West Point, West Haven, Marriott-Slaterville City, Plain City, and Farr West (Figure 1). We used the municipal boundaries dataset to calculate geometry for each municipality in ArcGIS and revealed a total of 129.3 km\({}^{2}\) for the urban areas and 110.9 km\({}^{2}\) for the exurban areas (Table 1). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Urban Municipal Name** & **Area (km\({}^{2}\))** & **Exurban Municipal Name** & **Area (km\({}^{2}\))** \\ \hline Sunset & 3.8 & West Point & 18.5 \\ Clearfield & 20.0 & West Haven & 26.8 \\ Roy & 20.3 & Marriott-Slaterville & 19.1 \\ Ogden & 70.4 & Plain City & 31.2 \\ Washington Terrace & 5.2 & Farr West & 15.3 \\ South Ogden & 9.6 & & \\ \hline Total & 129.3 & & 110.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Area of each municipality. Table 2 shows the calculated mean urban and exurban LSTs for several leaf-off and leaf-on dates. To perform the calculation, we first converted the at-sensor spectral radiance for the thermal band 6 of selected Landsat 5 images into at-sensor brightness temperature and then calculated final surface temperatures by correcting for spectral emissivities according to [35]. Emissivities were estimated using the NDVI thresholding method of [PERSON] et al. [36], using NDVI values that were calculated from reflectance images downloaded from the Climate Data Record (CDR) collection available on the USGS's EarthExplorer website. Clear LST data were extracted using a mask produced by the CFMask QA data provided with the Landsat reflectance data. Last, zonal statistics in ArcGIS were used to calculate the mean temperatures for the urban and exurban areas by date. The results show that for 75% of the dates calculated, average LST is higher in the urban areas by a range of 1.38-2.98 \({}^{\circ}\)C. The other 25% of the areas show a difference less than 0.1 \({}^{\circ}\)C.  
The elevation for these municipalities ranges from approximately 1286 to 1424 meters [37]. According to the National Weather Service, the local forecast office for Ogden, UT is Salt Lake City, UT. We used this local forecast office as an estimate to describe our study area's conditions.