How do you prep in a power outage due to an over-capacity system and the heat/humidity combination is no longer compatible with human life?

Or go near big bodies of water, big lakes or ocean. Then you can cool cause there is temperature difference. If closer to mountain, then just go up to avoid heat build up(reduce 0.65 Celsius per 100 meters altitude)

Underground might not be feasible without AC if you don't have good insulation. During BC, Canada's heat dome 2 years ago, you lose ambient cooling slowly, and then everything starts to feel warmer even in the basement parking.

For urban area, just prep the shopping center into cooling centres(including local stadiums ) that can help cool many people with emergency AC/resting place.

I was going to say that heat map looks like a 1:1 for swamp or close-to-sea level areas that might not be able to dig in any economical way

Especially in Florida!