How to delete the weather channel premium pro app?

The same way you delete any other app; Hold your finger on it until it wriggles, then tap the “x” on it. If there is no “x” Go to Settings/Screen Time/Content & Privacy Restrictions/iTunes & App Store Purchases - Change Deleting Apps to Allow.

If it has a subscription don’t forget to cancel the subscription also! See→How to cancel a subscription from Apple - Apple Support