- The simplest is just having thermal mass to average day and night temperature. As long as the night is cold enough you can just stay in a brick or clay building with thick walls, preferably painted white.
- If you want to get a bit more advanced, you can use evaporative cooling, like Persian Yakhchāls [1].
- If you go high-tech, certain paints can cool surfaces down by a couple degrees (by radiating heat at frequencies that don't get absorbed by the atmosphere, thus breaking the equilibrium between heat absorption and heat emission).
Of course there is a point where those fail. Evaporative cooling is dependent on a low wet-bulb temperature and fails quickly in humid climate. Thermal mass needs temperature differences. Paints only buy you a couple degrees. In contrast an AC can be scaled to much higher temperatures.