Air temperature in complex urban terrain can vary. A large proportion of this variation originates from differences in thermal characteristics of materials that together make up the terrain. While roads and buildings can lead to higher temperatures in urban landscapes, trees and other green urban infrastructure can provide cooling. Hence, depending on the type, make and proportion of urban infrastructure (e.g. grey, green, blue), air temperatures will vary. During the summer of 2023-2024, a total of 127 air temperature and relative humidity sensors recorded data every 10 minutes between 9 December 2023 and 6 March 2024 in and around the Local Government Area (LGA) of Sydney. This generated 1,5 million of individual measurements in two streams. Stream 1 covers the microclimate across the entire LGA, while Stream 2 contains data recorded for special case studies. All sensors were installed on trees, 2.5 - 3.0 m above the ground. The associated research report includes detailed methodology, analysis of results, and the heat maps generated for the LGA, as well as conclusions and recommendations. This dataset contains data from Stream 1 as .xlsx file: description of the data (spreadsheet 1) and air temperatures recorded in 92 (spreadsheet 2) and relative humidity in 32 locations across the LGA (spreadsheet 2). Spreadsheets 2 and 3 were also provided as csv file. This dataset provides measurement locations, physical address, geographic location, species name, height and canopy density of trees at each location (n = 92). Where available, temperature data represent mean and absolute maximum and minimum values measured at each location. Stream 1 dataset was split into early and late summer due to large number of missing loggers. Data Note: Tair (°C) = air temperature measured in degrees Celsius, and the time and date are in Australian Eastern Daylight Time (AEDT).