The Weather Widget will only display information if the Location Services is turned on. If it is, then I would suggest double checking your permissions on your phone.
I have a similar problem like Rijald. The widget updates - from time to time - but i can not trigger it only by opening it - data will not update automatically, only from time to time - i'd say the frequency is more ten 1h. For example - yesterday the sun set here in Poland just before 5pm. When i checked the weather on my widget at 5:50 it was still displaying the sun icon and old temperature info. it got updated eventually - but it generally happens way to rarely. A few ways i can force the widget to update is: - power off and on BT on the watch (works almost every time) - switch of and on GCM (works most of the times) - trigger data transfer from watch level (works sometimes).
So this is super annoying...Is the widged designed this way? to update only once an hour-ish...? It used to be even worse before i deleted app, re-paired phone, etc. so even though i kinda know a workaround - its only a workaround and it seems to work only when connected to wifi which makes so much sense...... Ah, and it will not work without GCM actually opened - it says it requires connection with the app to display current weather if the app is off. So i need to keep it opened all the time. The same with "find my phone" option - won't work with GCM off. Any iphone users have the same issue? iPhone 6s in particular?