Full website administrators can choose your community's units of measurement preference from the "Settings" section in the Admin Control Panel. This setting will be used wherever measurements are displayed throughout your community website, like the weather's temperature.
In the "Settings" section, click on the "Community" tab. Within this tab, click on the "Formatting" tab.
Next, under the header "Units of measurement," click on the drop-down menu to select which option you'd like used on your community website. Lastly, click "Save."