A fan won't save you in 98 degrees. A neighbor might.

Quick answer: A fan is for comfort. The CDC says that once temperatures reach the high 90s, fans won't prevent heat illness. At that point you need air conditioning or a cooling center. And check on older or ailing neighbors at least twice a day.

Most people get this backwards. They worry about their own house and never think about the guy two doors down who's 79, lives alone and won't run his AC because the electric bill made him wince last year.

The National Weather Service counts extreme heat among the leading weather-related killers in this country. It doesn't make the news the way a tornado does. It just works quietly, in closed-up houses, on people who didn't want to bother anyone.

What a fan actually does

A fan doesn't cool a room. The motor adds a little heat, if anything. What it does is move air across your skin so sweat evaporates faster, and evaporation is what cools you.

That's why a fan feels great at 85 and does very little at 98. In high humidity, sweat doesn't evaporate well, so the fan has less to work with. Older bodies and some medications can handle heat worse, too. Ask a pharmacist whether anything in your cabinet affects heat tolerance.

Turn the fan off when you leave the room. It's cooling you, not the furniture.

A few ways to get more out of one:

• At night, if it's cooler outside than inside, put a fan in one window facing in and open a window on the far side of the house. You're pulling the cool air through.
• During the day, do the opposite. Shut the windows and close blinds or curtains on the sunny side. A house that's been sealed against the afternoon holds its cool.
• On your body, a cool wet cloth on the neck and wrists, a cool shower, or feet in a tub of cool water does more than any breeze. Fan plus damp skin is the combination that works.

When to run the air conditioning

Run it. Don't be a hero.

The Department of Energy suggests 78°F when you're home as an efficient setting. That's a setting for a healthy adult watching the bill. If someone in your house is elderly, very young or sick, ask their doctor what temperature they need, and don't let the thermostat be the argument.

If the whole house is too much to cool, pick one room, usually the lowest and shadiest, and live in it. A window unit in one bedroom beats a central system that's losing the fight.

Check the equipment in May, not in the first week of triple digits. Swap the filter. Run it for an hour and make sure the air coming out is actually cold. Repair companies get booked solid when the heat arrives, and you don't want to be on a waiting list at 4 p.m. in July with a dead compressor.

If the power goes out and the AC goes with it, the clock is running. Plan to leave before the house gets dangerous, not after. The same advice applies to a long outage, which is covered in What a Week Without Power Actually Takes. And if you're thinking about a generator to run a window unit, read Twenty Feet From the House and Other Generator Rules first. Carbon monoxide kills people who were only trying to stay cool.

Cooling centers: find one before you need one

A cooling center is just an air-conditioned public building opened for people who have nowhere cool to go. Cities and counties set them up during heat emergencies, often in libraries, community centers or recreation buildings.

To find yours, call 211, or check your county emergency management page or your city's website. Do it now and write the address on the fridge.

Then call before you go. Ask four things:

• What are the hours?
• Is it wheelchair accessible?
• Are pets allowed?
• Is there transportation if someone doesn't drive?

Pets are the one that trips people up. Plenty of centers don't take them, and some people won't leave a dog in a hot house. Better to know the answer ahead of time.

No cooling center nearby? Libraries, malls and movie theaters work too. The goal is a few hours in real air conditioning. Even that gives the body a chance to recover.

Go early. A house that's been baking since morning is harder to leave at 5 p.m. when you're already tired and foggy. Take water, any medications, a phone charger and something to read.

And if your neighbor doesn't drive, offer him a seat in your car. That's the whole plan right there.

Checking on the neighbors

CDC guidance during extreme heat is to check on adults 65 and older and people with chronic illness at least twice a day. That means a knock in the morning and another in the evening.

Think about who's on your street:

• Anyone older who lives alone
• Anyone with a heart, lung or kidney condition, or a medication list as long as your arm
• Families with infants
• Anyone whose AC you know is broken, or who never turns it on

Knock. Don't text. A person who's feeling confused or weak won't always answer a message, and a text doesn't let you see how somebody looks.

Bring something. A bag of ice, a few cold bottles of water or a spare box fan makes it a visit instead of an inspection. It also gives a proud man a reason to open the door without feeling checked up on.

Ask plain questions. Is the air running? How hot is it inside? Have you been drinking water? If he's a stubborn type, and the ones at risk usually are, offer a ride to a cooling center and ask again tomorrow. Don't argue. Just keep showing up. Respect his pride, but don't let it decide the outcome.

A cheap thermometer on the wall of his living room settles a lot of arguments. If the reading is climbing into the 90s, that's my rule for "you're coming with me."

Know the signs

Heat exhaustion looks like heavy sweating, cold, pale, clammy skin, a fast weak pulse, nausea, dizziness, headache, muscle cramps or fainting. Get the person to a cool place, loosen clothing, apply cool cloths and give sips of water. Get medical help if it doesn't ease or it gets worse.

Heat stroke is an emergency. The body temperature hits 103°F or higher. The skin is hot and red, dry or damp. The pulse is fast and strong. There's confusion, slurred speech, or the person passes out. Call 911. While you wait, move the person to a cooler place and cool them with wet cloths or a cool bath. Don't try to force fluids into someone who's confused.

If you knock and nobody answers, and you have reason to worry, call the person's family. If you can't reach anyone, call your local non-emergency line and ask for a welfare check. If you can see someone down or in distress, call 911. Don't break in yourself unless you're sure it's life or death and you've got no other choice.

Never leave a child or pet in a parked car, even for a minute.

Do this before the first hot week

Put a thermometer in your house. Find your cooling center and call it. Make a list of the three neighbors you'll check on, with phone numbers. If your parents live far away, What Your Parents Need Before The Next Three-Day Outage covers what to set up before the power goes down.

Heat doesn't announce itself. Knock anyway.