The data of weather and Wet-bulb globe temperature (WBGT) for the summer of 2020 in Tokyo and other areas including local venues has been prepared by Tokyo 2020 Organizing Committee and published on the ISSF website.
While the composition of the data is generally same as last year and the year before, Tokyo 2020 OC has added detailed hourly data regarding weather such as temperature this time.
The data can help you for your preparations as well.