The single best place to escape dangerous heat is any air-conditioned building. Even spending two or three hours in air conditioning can meaningfully lower your core body temperature and reduce the risk of heat-related illness. If your home doesn’t have AC, head to a public library, shopping mall, community center, or a designated cooling center in your area.
Why Air Conditioning Matters Most
Your body sheds heat through four routes: radiation from your skin (about 60% of total heat loss), sweat evaporation (about 22%), and smaller contributions from convection and conduction. All of these depend on there being a temperature difference between your skin and the surrounding air. When outdoor temperatures climb above your skin temperature, radiation and convection stop working entirely, and your body becomes completely dependent on sweat evaporation. If humidity is also high, even sweating fails.
Lab studies have confirmed this. Researchers once theorized that humans could tolerate a wet-bulb temperature (a combined measure of heat and humidity) up to 95°F. But controlled experiments at Penn State found that young, healthy adults hit their limit well below that, between about 77°F and 87°F wet-bulb depending on humidity levels. In plain terms: the combination of heat and humidity becomes unmanageable far sooner than most people assume. Air conditioning is the only reliable way to create an environment where all your cooling systems work.
Where to Find Free Cooling Spaces
During heat emergencies, most cities open designated cooling centers. These are typically located in public libraries, recreation centers, community centers, and low-barrier shelters. Public libraries are especially accessible since they’re free, open during regular business hours, and available in most neighborhoods. Shopping malls, movie theaters, and large grocery stores also work as informal cooling shelters.
If you or someone you know is experiencing homelessness, day centers often provide more than just cool air. Many offer showers, restroom access, laundry facilities, phones, computers, and emergency clothing. Low-barrier shelters provide similar services along with case management. Your local health department or 211 hotline can help you find the nearest option.
Cooling Down at Home Without AC
If you can’t leave your home, fans help, but only up to a point. The CDC warns that at indoor temperatures above 90°F, a fan can actually raise your body temperature by blowing hot air across your skin faster than your sweat can cool it. Below 90°F, a fan pointed directly at your skin speeds evaporation and provides real relief.
Water is your most powerful tool at home. Because water conducts heat 100 times faster than air, even a cool (not ice-cold) shower, wet towels on your neck and wrists, or soaking your feet in a basin of cool water will pull heat from your body far more effectively than sitting in front of a fan. If you have a bathtub, filling it with cool tap water and sitting in it for 10 to 15 minutes is one of the fastest ways to bring your temperature down. Repeat as often as you need to throughout the day.
Keep blinds and curtains closed on sun-facing windows. Avoid using your oven or stove, which add heat to your living space. If your home has multiple floors, stay on the lowest one since heat rises.
Outdoor Shade Is Not Enough
Sitting under a tree or awning is better than standing in direct sun, but shade alone doesn’t lower air temperature significantly. On a 105°F day, shaded air might be 100°F, still well above your skin temperature. Your body can’t radiate heat into air that’s hotter than you are. Shade simply removes the added load of solar radiation hitting your skin directly.
If you must be outdoors, water features like splash pads, public pools, or even running water over your arms at a drinking fountain will cool you faster than shade alone. Wear light-colored, loose-fitting clothing made from breathable fabrics like cotton, which allows airflow and absorbs moisture. Tight or synthetic clothing can trap heat and sweat against your skin, disrupting your body’s ability to cool itself.
How to Recognize a Heat Emergency
Heat exhaustion shows up as heavy sweating, cool and clammy skin, dizziness, nausea, headache, a weak or rapid pulse, and muscle cramps. At this stage, getting to a cool environment and drinking water can reverse the situation.
Heatstroke is the line you don’t want to cross. It occurs when core body temperature reaches 104°F or higher. The warning signs shift: sweating may stop, skin becomes hot and dry, and confusion or loss of consciousness sets in. Heatstroke is a medical emergency. If someone becomes confused, can’t drink, or loses consciousness in the heat, call 911 and begin cooling them immediately with whatever cold water is available while waiting for help.
Nighttime Cooling Matters Too
During multi-day heat waves, nighttime recovery is critical. Your body needs cooler hours to reset, and when overnight temperatures stay elevated, heat illness risk compounds with each passing day. If your bedroom stays above 90°F at night, sleeping there with only a fan is not safe. This is when it’s worth staying with a friend or family member who has air conditioning, or finding an overnight cooling shelter.
Even a partial solution helps. Sleeping with damp sheets, placing a shallow pan of ice in front of a fan (when the room is below 90°F), or sleeping on the lowest floor of your home can make the difference between restful recovery and waking up already heat-stressed.