SAN FRANCISCO – Growing up, Anastasia Michaels remembers her family using "San Francisco air conditioning."

"Open the front door and the back door in the evening and hope there was a breeze," the Fog City native said. But the weather has changed since she was a child.

"Then, the heat waves would only last three days before the summer fog came back. Now we have started getting four- or five-day heat waves, so we got a small window air conditioner for the summers," she said (though they haven't installed it yet).

For much of the country, air conditioning is a way of life amid scorching summer heat waves, but millions of Americans like Michaels still live without it. In traditionally cool coastal cities such as San Francisco, Portland and Seattle, air conditioning is especially uncommon: only 45% of San Francisco homes and 53% of Seattle homes have it.

Mild climates make this possible (this week for example, lots of San Franciscans sported long sleeves and looked at a weekend high of 68 degrees). But when temperatures do spike, many in these areas still use old-fashioned strategies for staying cool. Those strategies may help people across the nation living without air conditioning, people who are temporarily without power or people who are just trying to cut down on their energy footprint.

But experts warn that when temperatures reach dangerous levels, the heat is nothing to be trifled with, and access to air conditioning can be a matter of life or death for some people. This is generally when temperatures rise above 90 degrees, but even temperatures above 80 degrees for long periods or when it's humid can be dangerous.

Take heat seriously, it can kill

First, take heat seriously because it can sicken and kill. That’s especially true if temperatures remain high for several days and when there’s no nighttime cooling. The elderly and people who don't have access to air conditioning are especially vulnerable, but everyone is at risk, experts warn.

"The stresses on your organs to keep you alive when it’s really hot are intense. When temperatures drop at night, your body has a chance to recover,” said Bharat Venkat, director of the UCLA Heat Lab. “When you don’t get that it’s pretty serious.”

Experts emphasize the need not just to cool off in hot weather but also to drink plenty of liquid, because dehydration can severely damage health.

It's not just deaths that spike during and after heat waves, said Alexandra Heaney, a climate and health epidemiologist at the University of California, San Diego who is collecting data about heat-related emergency room visits and deaths.

“When we get to these really high temperatures we see a big increase in mortality rates, but we also see really large increases in hospitalizations," she said.

To cool off and give the body a chance to take a break, consider visiting libraries or, for older people, adult day centers, or anyplace where your body can cool off in air conditioning. Make sure to check in on older friends and relatives and make sure they’re drinking enough water and are able to cool down.

Don't try to simply power through a long heat wave if you don't have access to air conditioning – it's simply too dangerous, said Ian Neel, a physician and geriatrician at UC San Diego Health. “Maybe you have friends whose houses you can go to if they do have central air.”

Close window shades and curtains during the day

When it's hot, the first rule is to keep out as much heat as possible. That means closing blinds and curtains during the day. This is especially true of east- and west-facing windows. You can throw open the windows at night.

Studies show medium-colored drapes with white plastic backings can reduce a room's heat gain by 33%.

If you don't have blinds and your curtains are sheer rather than light-blocking, there's always the old dorm-room trick of tacking a blanket over a window. Not pretty, but your home will stay cooler. Note that in humid areas the air will stay cooler, but it won't be dry in the way air inside an air-conditioned space is. 

Open windows at night

If you live in a dry heat area, open the windows when temperatures begin to fall at night, using screens to keep the bugs out and let cool evening air in. If you don't have screens, consider getting inexpensive adjustable window screens.

Keeping ceiling or other fans on at night lets the cooler night air circulate throughout your home, allowing you to start the day at a cooler temperature.

Use ceiling fans

"Fans use very, very little energy," said Jennifer Amann, a senior fellow with the nonprofit American Council for an Energy-Efficient Economy. For those with air conditioning who also want to keep costs down, they also allow you can turn up the air conditioning temperature a degree or two while keeping things comfortable by creating a wind chill effect.

Remember to turn fans off when you're not in the room. "They cool people, not rooms," Amann said.

Keep interior doors open

Keeping interior doors open at night allows the air temperature in your home to equalize, which helps bring temperatures down slightly overall. 

Note this only works if you're not using air conditioning in your bedroom. If you have room-specific air conditioning, close the bedroom off and have one cool room while allowing the rest of the house to cool naturally overnight.

Sleep in the basement

This might seem excessive, but in the Pacific Northwest, which has some of the lowest air conditioning rates in the country and has been beset by heat domes in recent years, some people move bedding down to their basements or even their apartment building's underground storage and parking level, where temperatures are much cooler.

Run the bathroom exhaust fan

When you shower, run the bathroom exhaust fan longer than you typically would. You want all that hot, humid air to end up outside and not warm up your home.

Dry laundry inside

If you've got a washer-load of clean clothes and a drying rack, you're in luck. Do what your great-grandmother did and put the rack up in the living room and drape the damp clothes over it to dry. As they do, evaporative cooling lowers the temperature in the room (as long as the windows are open so the moist air can get out). 

If rack-dried clothes feel too stiff or scratchy, you can wait for them to dry and then toss them into your dryer on the unheated "fluff" setting to loosen them up for a few minutes. In humid-heat areas, consider setting your dryer on its low setting.

Spritz away

Fill a clean spray bottle with cold water and very lightly spritz your sheets. You don't want them soaked, just misted. This makes for a nice cool bed. The same can be done to people, if they don't object.