Why does my Garmin instinct and Fenix 6 always show weather as partly cloudy?

I'm having this exact same issue.  My phone's weather app says that it is sunny in my locatio,  even showing me a big animated sun. On the garmin weather widget on my fenix 6 it says partly cloudy.  The watchfaces I'm using all say partly cloudy.  I've checked the location in garmin connect and set to gps and fixed knowing that both the locations are sunny. What's wierd is that the temperature seems to be correct and updating but the weather condition itself is stuck on partly cloudy.  

I'm adding some photos to compare what I'm seeing

Hello,
Have you found a solution? I have exactly the same problem as you.
Thank you for your help.

The weather shown on my F6xPS Garmin weather widget is from a weather station about 60 km away. On the wearables, you don’t the the source where the weather is taken from, but I can see it on my Edge 830 (same source, but with displayed location). Perhaps that is an explanation for your problem.

I've purposely changed the location settings to manually stay on a different town father from me and that seemed to do the trick.  For some reason,  in my immediate area,  the weather station is either inaccurate or Garmin is suggesting I move to a more sunny area.  

This is a really useful explanation.

There have been numerous discussions inn this forum over the past couple of years on the weather data and as far as I know, this is the first clear explanation from Garmin.

People have been theorising which weather app on their phone is responsible and even that the watch receives data direct from phone masts!

It might make sense that Garmin Connect uses data from a chosen app but I guess this is just the way it is. I find the weather data a bit 'approximate' for my location but have learned to live with it.