Weather in Celsius would be good. Fahrenheit isn't used in Europe at all.
You didn't mention what app or watch face you're talking about, but in many (all of mine), F or C is based on a setting on the watch itself.
"Setting>System>Units>Temperature Units" in most cases.
Thanks for the reply. I have the Glance Watch Face and the Venu Sq Garmin. Your advice worked. Thank you so much. Love the watch face.
I've never used Glance. I just have a bunch of apps that display the temperature and use the system setting in all of those and this is a common question I get.