I noticed if the Weather app on the iPhone is set to the current location, and a weather complication is set on the watch, location services is constantly on the iPhone, which causes the iPhone to always be warm (obviously some battery drain as well).
I had a Series 2 AW, and the fix was to add the city, then select this rather than the current location. Location would then pop up when using weather, then go.
With the Series 3, this doesn't happen and I have to set location to never (for the weather app) and then add a city.
The phone isn't warm anymore, and the Watch battery lasts longer.
Both only reset a few days ago (restored, without backup) so I suspect this happens to everyone.
Hope this helps someone
I had a Series 2 AW, and the fix was to add the city, then select this rather than the current location. Location would then pop up when using weather, then go.
With the Series 3, this doesn't happen and I have to set location to never (for the weather app) and then add a city.
The phone isn't warm anymore, and the Watch battery lasts longer.
Both only reset a few days ago (restored, without backup) so I suspect this happens to everyone.
Hope this helps someone