3 steps to cool your bedroom without AC, and all you need is a towel

Summer nights have a way of turning your bedroom into something that resembles a sauna more. You’re tired, you keep kicking off the sheets, and no amount of lying still seems to help. If you’re stuck with a broken AC, astronomical electricity bills, or just don’t own a window unit, there may be a low-effort fix in your bathroom linen closet right now.

John Lawless, a home heating expert at BestHeating, says there is a way that only needs a towel and some cold water. According to Lawless, one way to cool a room down is to open a window and hang a damp towel or sheet in front of it after soaking it in cold water. The moist fabric has to let the warm air from outside pass through it. As the air passes through the fabric, it loses heat before it enters your space.

Why your fan might not be enough
Most Americans reach for a fan the moment temperatures climb, and it makes sense: fans are cheap, widely available, and create an instant breeze. But there's a catch. U.S. Department of Energy notes that fans on their own do not actually lower the temperature of a room. They work by creating a wind chill effect on your skin, which makes you feel cooler, but the air itself stays just as warm. On nights when the heat is genuinely intense, that distinction matters. A fan circulating 85°F air is still circulating 85°F air, no matter how fast the blades spin. That's where the damp towel comes in. Pairing a fan with a damp towel hung nearby, or simply using the towel at an open window with no fan at all, introduces actual evaporative cooling into the equation, bringing the air temperature itself down rather than just moving warm air around.


Why this actually works
This is not some ancient household magic; the science behind it is well known. The U.S. Department of Energy explains that evaporative coolers (also called swamp coolers) operate on this principle: outdoor air is passed over water-saturated material, the water evaporates and cools the air by 15° to 40°F before the air enters the home. A damp towel in front of a window is a stripped-down version of the same technology.

Water needs energy to evaporate. It takes it right from the heat of the air around it. When warm outside air passes through the towel's wet fibers, it releases heat, triggering evaporation and leaving the towel feeling cooler. This approach works especially well in low-humidity areas where evaporation happens quickly, said the U.S. Department of Energy. If you live in a humid climate like the Southeast, it will be more limited, and the towel may be adding some unwanted moisture to the air.

Why your bedroom temperature matters more than you think
Not only is it uncomfortable to sleep in a hot bedroom, but it also affects the quality of your sleep. A 2023 study, ‘Nighttime ambient temperature and sleep in community-dwelling older adults,’ published in Science of the Total Environment, tracked older adults for 18 months with wearable sleep monitors and bedroom sensors and found that the most efficient sleep occurred when nighttime ambient temperatures were between 68°F and 77°F (20–25°C). That same study found a clinically significant 5 to 10 percent drop in sleep efficiency when bedroom temperatures rose above that range. If your room is too hot, your body struggles to do what it needs to do naturally while you're sleeping, and the quality of your sleep suffers.

How to set it up
The technique is simple, but a few details make a world of difference.

Fill your sink or a large bowl with cold water and completely submerge a bath towel. Then squeeze it out thoroughly. According to Lawless, the towel should be damp but not soaking wet. If it’s too saturated, air will not be able to penetrate it, and the room could end up feeling muggy rather than cool.

Hang the towel straight out of an open window. You need a little airflow for this to work, but even slight air movement will start the evaporation process, Lawless says. Alternatively, you can drape the towel across a doorway. Once it dries out, simply dampen and hang it up again. On very hot nights, this may need to be done more than once.

Dealing with the heat that built up during the day
What makes hot nights worse is how much heat gets trapped inside during the day. Sunlight heats the air around windows all day, and when you close your curtains at night, that heat stays trapped inside, according to Lawless. Pulling your blackout curtains or blinds during the hottest part of the afternoon, before the heat has a chance to build up, can make a noticeable difference by the time you’re ready for bed, and will make the damp towel method even more effective.

A few honest caveats
This trick has real limitations. According to the U.S. Department of Energy, evaporative cooling works best in low-humidity climates, but the effects of evaporative cooling are lessened if the air is already saturated with moisture. It’s also no substitute for air conditioning in a serious heat event.

That said, for mild to moderate summer nights, especially in drier parts of the country such as the Southwest or Mountain West, this method can provide enough relief to actually fall asleep. It is free, uses very little water, and does not require electricity. Sometimes the best solutions really are the simplest ones.