This applies to both the mobile app and the web app.
When zoomed out to level 4, graphs (such as temperature) only show 8 or 9 data points per day. For example, see Tempest
I think it would be useful to show more data points per day so that smaller fluctuations are visible.
Also, I think it would be useful to be able to zoom out more (e.g. level 5) and show a continuous graph as opposed to just high/low/average for each day. Perhaps there could be an option to show the data in either format.
As an example of higher resolution graphs which I think are helpful, see http://www.findu.com/cgi-bin/wxpage.cgi?call=DW2363&last=240