Weather on iOS always shows Cupertino no matter how many times I change

The small weather screen on your iPad is the “Weather Widget”. You can press on it and long hold, then edit and change the location. The widget will let you pick any city from your weather app or you can choose “my location”. If you choose “my location”, it will keep displaying Cupertino. Choose a city instead. If you don’t have any cities to choose from, add them to your weather app first.

Perhaps your refer to a Weather Widget. Touch-and-hold (i.e., long-touch) the Widget…

• If you wish to remove the Widget in its entirety, select Remove Widget.

• If you wish to change the displayed location to another city, select Edit Widget, tap Location then select the preferred city or Current Location.

If instead you are attempting to change the list of cities of interest within the Weather App itself - open the Weather App; within the associated sidebar you will see a list a locations for which a forecast has been configured. At top-right of the Weather sidebar, tap the ellipsis (“…”) icon - and from the menu tap Edit List. 

Each of your configured locations will now have an associated red “-“ button. Tap the button for each location that you wish to delete from the Weather App. When you’re finished, tap Done.