(Not the OP) "Uninhabitable" is a vague word, but I found it useful to think about this in terms of global stability. The US Dept. of Defense (not a traditionally environmentalist group, though perhaps traditionally alarmist) did a series of studies on this. Here's a recent summary: https://media.defense.gov/2021/Oct/21/2002877353/-1/-1/0/DOD...

Basically habitability and stability isn't just a matter of "will this land burn you alive" but also access to cropland and rangeland, clean water, or avoiding negatives like increased hurricanes and wildfires, or simply floods and droughts. Migration out of increasingly harsh areas is expected to fuel global instability, across large regions of the world at a time, often in some of the most populous or contentious areas.

While the DoD's regional analyses aren't released to the public, there are similar studies in academia... https://scholar.google.com/scholar_url?url=https://par.nsf.g... (that one does go into detailed definitions of habitability).

Basically the hot and humid areas of the world, like Southeast Asia and Sub Saharan Africa, are expected to spawn a lot of climate refugees.

I believe more detailed models are out there, but I haven't looked too deep.

For the right definitions of "soon" and "uninhabitable" most of the Indian subcontinent and south east Asia.

With only a little bit of snark: if you listen to insurers that would be Florida.