How does the app determine default location. It keeps starting using a deleted location.

Hello Dawilliams,

We see you have a question about the Weather app. The text belows covers a bit about the Weather app and Location Services: Check the weather on iPhone - Apple Support

Note: Weather uses Location Services to get the forecast for your current location. To make sure Location Services is turned on, go to Settings  > Privacy & Security > Location Services > Weather. Turn on Precise Location to increase the accuracy of the forecast in your current location.

You mentioned a deleted location. Are you saying you had a location added to your weather list and deleted it but it still appears when you open the app? When you try the steps below, does it appear in your weather list? Check the weather in other locations on iPhone - Apple Support

Check the weather in another location

1. Open Weather, then tap  in the bottom-right corner of the screen.

2. Tap the search field at the top of the screen, then enter the name of the city or the airport code.

3. Tap the location in the search results to view the forecast.

4. Tap Cancel to close the forecast, then tap Cancel to clear the search results.

Let us know! Take care.