Daylight visualization
The detail view for individual cities is a bit empty at the moment. If we don't remove it, perhaps we could do something interesting with it, such as a visualization of where the sun is wrt sunset/sunrise at the moment.
This app is an interesting example of something in this direction that's both informative and visually compelling:
If we were to do something like that, it could also be interesting to have a smaller version of it inline in the rows, instead of the background color on the time.