Asklemmy

I assume you are looking for passive methods that aren't air conditioning.

As others have said, thick walls that have a thermal mass. It helps if you open the building at night to help cool the walls.

The structure should be as light as possible, both the walls and roof, to reflect back light.

Windows should have large awnings so direct light doesn't enter during summer. Everything should be in the shade.

If you can, you can create a solar chimney by having a large and dark chimney on the south side of your building. Set your building up so that there is a natural air intake which comes from below ground, so you naturally pull in cool air.

Thick (~1m) mudbrick walls. I lived in a house like that for 2 years, it felt cold inside in summer.

Install solar panels on the roof and use the power to run air conditioning.

Drink a ton of water.

Plant as many plants as possible. Trees are best. Make sure to use species native to your region that deal well with the prevalent weather.

Not sure how your buildings are built over there so this may not apply. But an exhaust fan for the space between the ceiling and roof does wonders to cool a house after a hot day. Those attic spaces get crazy hot and hold the heat well after the sun sets and it keeps your house hotter longer. This won't necessarily help with mid day heat, but help cool the living space as the sun goes down.

Take an undershirt you're not wearing, get it soaking wet, drape it around your neck

Central air conditioning all summer long.

But before I had AC, on hot nights I'd put a cold damp rag on my feet to fall asleep easier and that really worked. I'd also put a box fan in one of my windows pointed outside, and I'd also open a window in another room so that outside air would be sucked in through my home.

Chimney. If you have a chimney, open it.

Any air passing above will create a suction effect below and suck all the hot air out of the room.

I learned to be cool in hot temperature by being still, in the shade, with a breeze, it's very hot and humid here but also windy usually.

Trees help so much. It is noticeably cooler at the park than in the city.

In the house when there is not air conditioning, roofed porches and opening the windows with fans pulling air through the house helps.

There is research that shows that white coloured roofing causes increased heating elsewhere, so it's not a fix-all solution.

I live in Australia and during summer use a lawn sprinkler on the roof. Using a tap timer, it runs for 10 to 30 seconds every 10 minutes.

Just enough to wet the roof, so that the water evaporates and cools it down.

Other things you can do is growing creeper vines over a wall where the sun hits in the afternoon to keep direct sunlight off the wall.

If you have sash windows, you can open it at the top and bottom, creating a thermal airflow that will cool the house.

Adding sunshades and building housing with awnings makes a massive difference.

Lots of research associated with passive solar temperature regulation.

If it's not overly humid, evaporative air conditioners are a cheap to run way to keep cool. The personal units (Convair Classic etc) are typically about 50 to 80 watts, so a single solar panel, battery and inverter should guarantee safe, grid free cooling for one or two people.

Arabian here, uhh - it's insanely hot here too. Lol. Outside, i try to move to shade and trees as fast as possible, carry two water bottles all the time and relax in shadows when i can.

At home? ACs.

My advice isn't too useful sadly, but i hope you can use it a little.

drink water, loads of it; if you have to go out, always keep a bottle at hand. wear less clothes and keep your house fresh and ventilated, open all windows if possible. buy a/c for your bedrooms but use them just in the night, when you have to sleep. use fans where you have to work or stay during the day. to cope with the higher electric bill, consider installing solar panels on your roof, or a small wind turbine.

My English isn't Englishing atm, bear with me. Heat island effect is caused (amongst other things) due to sealed ground. So replacing asfalt roads, and even brick sealings with green space or even better water, should help regulate temperature. On top of this, instead of white roofs, green roofs are also a good option

Cover the windows from the outside (not inside) to stop sunlight raising the temperature through the glass. I use tinfoil.

Plants and trees

Reflectrix on the inside/underside of the roof.

1. It’s a cheap material.
2. It’s quick to install.

Besides that, better insulation and the use of high efficiency heat pumps.

It might be easier near the coast, but opening up windows during times of day where you can catch a breeze might help with the heat the house soaks up. Insect netting on windows may make this a more tolerable option.

Beyond this, the high ceilings in older style homes seemed to make things feel cooler, but I can't really confirm that. A lot of design aspects of older homes were meant to deal with heat, so it might not be trendy but works. I've seen one place with a sizeable indoor pond/pool in the middle of the ground floor, supposedly inspired by courtyard transpiration. The guy was an odd engineer.. no idea about longevity but it did stay cool in that place.

Plants to cut down on sunlight while giving you something nice to look at seems good. Maybe planters for vegetables etc on a flat roof if it's possible.

On top of white paint, if it's legal, try putting up some camo netting above the roof to provide shade on top of the reflectiveness of the white paint. Shades over windows.

Bucket of cold water, stick your feet into it.

Tin foil in the windows to reflect radiation.

Cold tap over inside of forearms and wrists (iirc ears work well too, but of course a more awkward reach if you're just using a bathroom tap).

I handled the heat by moving from Northern Australia to Tasmania.

There must me much cooler places in India?

Shade is everything. Tree shade is the best, because trees transpire, cooling the ground beneath them even more than shade would alone.

Inside your house (depending on what kind of home you have), you can also take a look at your overall energy efficiency, including windows, doors, insulation in walls and attic, and weather stripping to seal all gaps

https://youtu.be/KDRnEm-B3AI

DIY paint. It will cool the surface to below ambient temperature.

how much air conditioning do you have? if you take public transport, is it air-conditioned?

Trees are great.