The power went out in my apartment last July when it was 102 degrees outside. The indoor temperature climbed from 72 to 88 in under two hours. We had no AC, no fans, and no idea how long the outage would last. Here is what I learned.

First five minutes: Contain the cool

Close every window, blind, and curtain. Do not open the refrigerator or freezer unless absolutely necessary. A full freezer keeps food cold for about 48 hours. A half-full one lasts about 24. Every time you open the door you lose hours of cold.

Close doors to rooms you do not need to be in. Pick one room to cool — preferably the basement or a north-facing room — and stay there. Your body heat will warm a small room faster than you think.

Cooling your body without AC

Wet a towel or T-shirt with cool water and drape it over your shoulders or around your neck. The evaporation pulls heat away from your skin. This works better than a fan alone because fans just move hot air around — they do not actually cool you.

Put your wrists under cold running water for thirty seconds. The blood vessels are close to the surface there, so cooling your wrists cools your circulating blood. It sounds trivial but it genuinely helps.

Take a cool shower — not cold. Cold water makes your blood vessels constrict and actually traps heat inside your body. Cool-to-lukewarm water is best.

Food and water

Drink water constantly. By the time you feel thirsty you are already mildly dehydrated. Skip the caffeine and alcohol — both make you lose fluids faster.

Eat foods that do not require cooking. Canned fruit, cold sandwiches, cereal with shelf-stable milk. If you must cook, use a camp stove outside — never use a gas stove indoors for heating or cooking during an outage, it can produce carbon monoxide.

When to leave

If the indoor temperature passes 90 degrees and you have elderly people, infants, or anyone with a heart condition in the house, go to a cooling center, a library, a mall, or a friend’s house with power. Heat stroke can kill faster than most people realize.

Symptoms to watch for: confusion, rapid pulse, hot dry skin, nausea. If someone stops sweating in extreme heat, that is a medical emergency.

We lasted four hours before we decamped to a movie theater. The theater was freezing. Best movie experience of my life, and I do not even remember what we watched.