How do I put this app on my iPad? It’s not in the App Store.

Hello cosmo3381,

Thank you for reaching out to Apple Support Communities.

These steps may be able to you locate the app in the App Library:

"Find and open an app in App Library

1. Go to the Home Screen, then swipe left past all your Home Screen pages to get to App Library.
2. You can also open App Library quickly by tapping , the rightmost button in the Dock at the bottom of the screen.
3. Tap the search field at the top of the screen, then enter the name of the app you’re looking for.
4. Or scroll to browse the alphabetical list.
5. To open an app, tap it.

If a category in App Library has a few small app icons, you can tap them to expand the category and see all the apps in it."

More details can be found here: Find your apps in App Library on iPad

If you still can't find it, try downloading it from this link: Weather on the App Store

Hopefully this helps.

Cheers!