lots of good tips in here. something i would do when i felt like all my tricks weren't cutting it was to put on swimming stuff and then take a cool shower, but not dry off very much. then id lay in some shady spot under / near a fan. even with higher humidity, that can be very cooling in the short term. i set up a hammock on a porch with a fan and would just do that repeatedly to get through the hottest parts of the hottest days.

cool water running over your back, neck, pits, groin cools your body temp quickly.

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other, less drastic: shade trees pull heat from their surroundings with evapotranspiration. si the effect of shade plus being a heat sink. it can be significant with lots of trees. parks a good idea to visit. leaving the city can be good, as they tend to create a heat dome from the lack of plants and all the buildings just absorbing heat, activity creating heat, etc.

don't expose your skin to the sun any more than you must. cover your head or stick to the shade. the sun cooks your ass. wear light color/light weight fabrics that are baggy and allow breezes. breezes save your ass.

mid day siesta. don't gotta sleep, but do not be active. hottest parts of the days tend to be late afternoon. have a plan.

if you can find a way to be cooler at night, sleep is way easier and you will be more rested/less prone to heat exhaustion/heat injury.