Weather provider?
http://openweathermap.org/

Update frequency?
about once every hour
→ if there is internet connection
→ connection to watch
→ coarse location fix (to find city for local weather)

Why 2 bubbles?
Current local weather: shows the temperature and weather condition graphic for your current location. If you make the bubble bigger it will also display the forecast low/high temperatures too. Night graphics are used after sunset.
Other weather: it can show tomorrow’s forecast for the current location, or you can enter any geo-location for its current conditions. If bubble size permits the name of the location or the day is also shown with the low/high temps. Will only show day-time graphics.

Hollow circles?
In ambient mode or if hollow bubbles are selected, the color of the border will show you the weather conditions instead of the graphics:
→sunny=yellow
→cloudy=light blue
→rainy=green
→stormy=red
→snowy=white
→foggy=gray

How to add weather bubbles?
Only available to Premium users.
Please see https://plus.google.com/111815032990260235809/posts/At2tdUXrfLJ

Celsius vs Farenheit?
Tap the current local weather bubble in the Wear Cloud Editor