Clearly you’re doing something strange somewhere because values don’t magically round themselves. EDIT They can if there’s unit system conversion involved!
Paste this into the Template Editor and you’ll see the difference.
{{ state_attr('weather.your_weather', 'temperature') | round(0, default=-99) }}
{{ state_attr('weather.your_weather', 'temperature') }}
By removing the round filter from the example I posted, your modified version simply copies the values from the met.no integration unchanged. I demonstrated that in my previous post where the third Weather card shows the same values as in the first Weather card. EDIT Because my system is configured to use the metric system.
Clearly the Weather card doesn’t round the values, otherwise it would have also rounded met.no’s values so something is rounding them.
The clue that you have done something odd is the fact that you originally showed a screenshot where only the current condition was displayed and the temperature was NaN (Not a Number). That’s representative of a misconfiguration somewhere in the card and/or Template Weather. EDIT Possibly due to misconfiguration but the real reason for the “magical rounding” is described below.