[palm-tree]

"Years of abnormally low rainfall" - at what point does "abnormal" become normal?

[thaumasiotes]

Never. That might make it sound less like an emergency.

For example, one of the first things you'll read in the wikipedia article on "Drought" is this:

> The longest drought in recorded history started 400 years ago in the Atacama Desert in Chile and still continues.

[Waterluvian]

So long as a settlement’s reason for its location has shifted drastically, never.