Weather data never changes. Ie temp, wind etc
Which weather data? In the watch or in the activity?
In watch
Not sure what activity is
Activity is when you record a run, bike or other activity type. For each activity you will see the weather.
Is it in a watch face or the weather widget?
Read more here what you can do: https://support.garmin.com/en-US/?faq=Mxs4eRXzRdAYJ0h7yyWaj9