[changing1999]

My only criticism of this approach is that it asks highly sensitive users to learn a critical keyboard shortcut that will not work anywhere else. What will happen if users attempt to triple press "shift" on any other surface that doesn't support this? Because that's highly likely.

Instead of introducing a new (hidden) shortcut, I would rely on clear visual cues and intuitive (meaning, already common) interactions. E.g. opening the form in a modal; clicking anywhere outside of this modal closes the modal and loads the weather page. The clickable background should be clearly identified as a special feature, e.g. tiled text "exit page" all over it.