How does Apple's mobile phone weather set the current city?

Apple's mobile phone settings show that the current city weather is as follows:

Tools/raw materials:

IPhone 12, iOS 14, set v3.1131524.

1. Open the phone settings and select Privacy, as shown in the following figure:

2. Start the location service and select the weather, as shown in the figure below:

3. Check the life cycle of the app or widget, as shown in the following figure: