I grew up without AC in Florida.

Sit in the shade with a fan, be still. If in the shade and a breeze, and not moving around, a pretty high temperature is comfortable.

Go to places with cold AC or to cold springs to get cold, it will last awhile after you leave.

If it gets cool at night, open your window at night to let in the cold air, close it in the morning to keep that air in for the morning. But once it heats up inside, you are better off with ventilation - open windows on both sides of the house and run fans, to move air throughout the house.

If it’s dry where you are (it doesn’t work here) get wet and let evaporation cool you. Even here you can get wet and stand naked in front of a fan you will get cold.

STAY HYDRATED.

I was previously convinced that taking cold showers was my only saving grace during hot summers, but this year I got the advice to try to take a warm shower a short while before bed, and I’m surprised to say that it has helped. This is for high 20s though so YMMV for sure.

Other things that help:

• Open windows when outdoor temperature is lower than indoor temperature, and try to get a cross breeze going if possible
• Keep light out of the house by closing blinds during the day
• Wear linen clothing and use linen bedding, this material works better for warm conditions
• Fans help reduce perceived temperature by several degrees

If you’re in a humid environment and you have a way, dry the air. It makes any other cooling thing you do more effective.

Run cold water over your wrists when you’re starting to get hot.

Wet T-shirt and sitting in front of a fan.

We naturally cool our bodies by sweating.

You can sort of hack that process by getting a t-shirt wet, putting it on, and allowing the moving air to help speed up the evaporation process.

WARNING: NOT FOR USE IN HIGH HUMIDTY.

Adding more water to an already hot and humid situation risks a Wet Bulb.

When I worked in a restaurant kitchen, we used to soak rags with water and freeze them in the walk in freezer, then once it’s nice and frozen we’d wear the rag around our necks.

There’s large blood vessels in the neck feeding your brain, so if you’re able to cool down the blood there, it’ll spread to the whole body surprisingly fast.

I actually managed to get cold in hot humid july summer in the kitchen with that method.

Windows open at night. Curtains or blinds shut during the day.

At my family cottage, we had it for over 40 years before getting portable ACs. Generally we just avoided the heat waves. Cold waterbottles in between your neck and shoulders really helps circulate the cooled blood throughout your body. We ended up getting portable ACs one year because we were spending a week there and it was over 95f every day. A few years later one of us took a paid early retirement package and we used some of that money to get central AC, best upgrade for our cottage ever.

If you have cool nights, setup fans up at night to bring the house down to a lower temperature. Close everything up in the morning when the outside temp starts rising above your inside temp. If your place is insulated reasonably and there’s no excessive sun from windows, it will stay cool for the day.

Protip: Setup the fans in all rooms on one side of a chokepoint in your house/apartment (stairwell/hallway) to exhaust, to encourage airflow. Open up all the windows on the other side for intake. It’ll also help reduce pockets of hot air left over from the day before.

If you have a freezer and a fan, freeze a bunch of water bottles and then put them right behind your fan blades for a cheap AC-like chilly breeze. If you have enough bottles, you can cycle through them and refreeze as they thaw out.

Block out the heat and sun during the day. Have everything open during the night, with a tactical fan placed wherever it helps the most.

But this only really helps the first few days. After that it’s down to accepting the situation and being so tired that you fall asleep anyway.

I didn’t go through all the comments so sorry if thus is a duplicate.

Last year I learned that having a wet (not soking-weat) towel on your feet or your belly can keep you cool during the night. If you struggle falling asleep without a blanket and your’re to hot to sleep it might help.

I have a basement where I swear it’s 10°C colder than upstairs.

Never take a hot shower. In fact turn off your water heater if you can. The goal is to avoid having hot water in your pipes heating the house

At night cool your house down by opening windows and using windows fans. I have a two story house. Heat rises so I’ll place window fans blowing out in the upstairs windows and fans blowing in upstairs. In the morning close up the windows and close curtains and shades over the windows that receive direct sunlight. If you have a room that gets hotter than the others shut the door to that room or hang a curtain over the doorway. My hot water tank is in a first floor room so I isolate that room and leave the windows open. Have a ceiling fan? Make sure it’s blowing in the right direction. Most have a switch so you can alternate direction it blows the air. Not always practical but soaking your feet in cool water will lower your body temperature. Much like coolant cools a combustible engine car your blood circulates through your body distributing heat. Personally I avoid using AC while driving as much as I can. It’s my opinion that when we get used to such comforts we suffer without them. I do have a window unit but use it only on the hottest nights. One last thought. Some lights or appliances in your house may give off a lot of heat, feel around them to find which ones do and switch them off. You can’t do anything about your refrigerator (gives off a lot) I had a plasma TV that felt like a space heater and also used a lot of electricity