How do I change temperature units in Android wear weather app?
I contacted Fossil who said that the temperature units on the watch are based on the language setting you select when you set up the watch. If you select US English, then it will be Fahrenheit (probably the only language setting that uses Fahrenheit).

I am Canadian and there is not usually a Canadian English option and UK English has caused strange anomalies for me in the past. Plus I live in the USA, I just want Celsius and I don't think I'm the only one. I informed them that their solution for units is not adequate.

I will edit this answer if they get back to me with anything more useful or if they fix the issue and make it configurable.

I am using the accuweather app which I paid for years ago and I like it. But their android wear app is broken right now on my watch and they are aware of the issue and working on it, but it has been some time (plus their latest material design update took ALL of their flexibility out of unit selection so that is quickly becoming an issue).