The detailed weather forecast uses the shortest available timeperiods. For OpenWeatherMap it's always 3 hours, but for met.no it can be from 1 to 6 hours depending on location and time span.

Graph view (Meteogram)

Graph view and day colors

With the graph view you get a quick look at the next 24 hour forecast. The white line is the temperature and the blue columns are percipitation. If a min-max forecast is available for percipitation, the blue columns are minimum and the white columns maximum percipitation. In the top view you see the details for the current weather forecast

You can select a day from the daily forecast to see the graph overview for the day. To go back to current forecast and next 24h meteogram, just press the selected day again to unselect it.

If you would like to see more detailed forecast for a time period you can touch the graph and a red line pops up showing you the selected time period. The detail view on top will now show you the details for the selected period instead of the current weather. Move your finger left/right while touching to move the red line and update the details on top. When you let go the details revert to the current time forecast.

This also works for any selected day, but when you let go, the details will revert to the daily "mid day forecast" for the selected day.