There's plenty we can do, but all interventions are somewhat limited in effect. With the trend of increasingly intense heat waves, we're likely going to have to do all of the non-AC interventions and install AC in lots and lots of places.

• Awnings to block sunlight from heating up spaces through windows
• Better ventilation systems which can more effectively pump in colder air from outside during the night
• Heat-reflecting paint to minimize heat gain from solar radiation
• More trees to provide local cooling/shade
• Ceiling fans to provide reduced perceived heat
• District cooling, when appropriate, to provide cooling at a higher energy efficiency

All help, but when the temperatures start hitting 40 C with high humidity, you're basically out of luck without an AC, that can pump out the heat and lower the humidity.