Our air conditioner died during the hottest week of the year in 2023. Ninety-eight degrees outside, ninety-two inside. The repair technician could not come for four days. I spent those four days learning more about keeping a house cool than I had in my entire life up to that point.

Windows are your thermostat

The most important rule: windows open at night, windows closed during the day. It sounds obvious, but most people leave windows cracked all day “for airflow.” When it is ninety-five degrees outside, that airflow is a convection oven. You are heating your house, not cooling it.

Open everything at sunset. Box fans in the windows — one blowing in on the shady side of the house, one blowing out on the sunny side. This creates a cross-breeze that flushes the hot air out and pulls cool air in. At sunrise — or whenever the outside temperature climbs above the inside temperature — close everything. Windows, blinds, curtains. Seal the house like a cooler.

Stop generating heat inside the house

Your oven produces as much heat as a small space heater. Do not use it. Your dryer vents hot air outside, but the machine itself radiates heat while running. Hang laundry instead. Incandescent light bulbs convert ninety percent of electricity to heat. If you still have them, swap for LEDs. Computers, gaming consoles, and large TVs pump out enough heat to warm a small room. Turn them off when not actively using them.

Cool yourself, not the room

A fan pointed at your body cools you by about four degrees through evaporative cooling — sweat evaporating off your skin. A fan pointed at an empty room does nothing but move hot air around. Point the fan at yourself. A damp cloth on the back of your neck or on your wrists — where blood vessels run close to the skin — amplifies the effect.

Sleep with a slightly damp sheet. It sounds miserable but it works — the evaporation pulls heat off your body all night. In the morning the sheet is dry and you slept through the worst of it.

The ice-and-fan air conditioner

Fill a shallow pan or bowl with ice. Position a fan to blow across the surface of the ice toward you. This is not an air conditioner — it will not cool a whole room. But it will cool the air directly in front of the fan by several degrees for about an hour. For desperate moments, it helps.

Longer-term fixes that cost less than AC

• Reflective window film. Blocks up to seventy percent of solar heat. Ten dollars a window, sticks on with water, removable in the fall. The difference is noticeable within minutes of applying it to a sun-blasted window.
• Blackout curtains. White-backed blackout curtains reflect heat back out. Dark-colored curtains absorb heat and radiate it into the room. The white backing matters as much as the thickness.
• Attic ventilation. An attic can hit 150 degrees in summer. That heat radiates down through the ceiling all night. A solar-powered attic fan — about two hundred dollars — vents that heat automatically whenever the sun is out. No wiring required.

Our AC was fixed on day five. But I still use most of these tricks at the edges of summer — May and September — when it is hot but not AC-hot. They work. Four days of trial by fire taught me that.