How does ios get system weather forecast data?

1) Open the settings of iPhone6 plus, and then select Privacy.

2) Select Location Services, slide down to find the weather, and turn this option on.

3) Go back to the settings page of iPhone6, select the notification center and turn on the switch of today's summary option.

4) After completing the settings according to the above steps, drop down the notification bar, and you can view the weather of the day in today's bar.