If the 100F heat comes with very low humidity (which is what I'd expect in AZ), it'd feel nicer than the weather we get in Kansas (except maybe for this year; this year was cooler).
The fact that the heat doesn't go away even at night is another issue. If the power ever fails for vulnerable populations, they're immediately in danger. There's no reprieve of night or insulation you can use to fully mitigate those conditions.