Our AC died during a heat wave two summers ago. Ninety-eight degrees outside, ninety-two inside, and the repair guy said he could come Thursday. It was Monday. I paced around the house feeling personally attacked by the air itself. My cat sprawled flat on the bathroom tile like she had been dropped from a height.

Four days later, when the repair guy finally showed up, I had learned a few things about staying cool without mechanical help. The surprising one: most of what people do to cool down actually makes them hotter.

The Fan Mistake Everyone Makes

Fans cool people, not rooms. A fan in an empty room is just an electricity-powered heater. The motor generates heat. The moving air makes you feel cooler because it speeds up sweat evaporation, but if nobody is in the room, turn the fan off.

Also: at temperatures above about ninety-five degrees, a fan can actually heat you up — like a convection oven. The air moving over your skin is hotter than your body temperature. In extreme heat, use fans only when you are in the room and only when the temperature is below body temperature.

The Window Strategy

Windows are your primary climate control tool without AC. The rules are:

• Open windows at night when the outside temperature drops below the inside temperature. Open windows on opposite sides of the house to create a cross-breeze.
• Close windows and curtains before sunrise. Once the sun is up, every window is a heat inlet. Blackout curtains or even a blanket tacked over a sunny window makes a measurable difference.
• If you have a two-story house, open upstairs windows on the downwind side and downstairs windows on the upwind side. Hot air rises and escapes upstairs, pulling cooler air in downstairs.

Body Hacks

Your body has a few built-in radiators. Target them:

• Wrists and neck. Run cold water over your wrists for thirty seconds. Wrap a cold, wet bandana around your neck. These are places where blood runs close to the surface — cooling them cools your circulating blood.
• Feet in cold water. Fill a basin with cool water, put your feet in. Your feet have a high surface area and lots of blood flow. This drops your perceived body temperature fast.
• Damp sheet. A slightly damp cotton sheet as your only covering at night. As the water evaporates it pulls heat from your body. This is basically how sweat works but more efficient because the sheet holds the water against your skin longer.

What Makes It Worse

• Opening windows during the day. Unless there is a strong breeze, you are just letting hot air in.
• Running the oven. Cook outside on a grill, use a slow cooker on the porch, or eat cold food. An oven adds thousands of BTUs of heat to your house that you then have to fight.
• Cold showers. They feel great but your body responds by constricting blood vessels and then overcompensating — you feel hotter ten minutes later. A lukewarm shower is better for sustained cooling.

I survived those four days. The cat survived too, though she gave me a look that suggested she held me personally responsible. When the AC came back on, I sat directly under a vent for ten minutes. I have never been so grateful for mechanical refrigeration.