Extreme heat

A phone call is not enough

The National Weather Service recorded 529 heat-related deaths in 2024, making extreme heat the leading weather fatality category that year. Most victims are elderly adults living alone. The consistent finding across heat wave mortality studies: in-person welfare checks save lives that phone calls do not.

When a person is experiencing heat exhaustion or early heat stroke, confusion and disorientation are common symptoms. They may not answer the phone. They may insist they are fine when asked. Only a face-to-face check reveals the actual condition: the person who is barely conscious in a 95°F apartment, or who cannot remember what day it is, or whose skin is hot and dry.

CDC's heat safety guidance for community members is straightforward: during a heat emergency, check on elderly neighbors, those with chronic medical conditions, and people who live alone. Go in person. If the person does not answer the door and you have reason to believe they are inside, call 911. A wellness check by emergency services is preferable to discovering someone has died from heat exposure.

Who is highest risk: adults over 65, people with heart disease, lung disease, diabetes, kidney disease, or mental illness, people taking diuretics, beta-blockers, antipsychotics, or anticholinergics, people without air conditioning, and people who live alone.

Cracked windows change almost nothing

NHTSA data shows that on a 90°F day, the inside of a car reaches 109°F within 20 minutes. On a 100°F day, it reaches 119°F. Cracking the windows by a few inches reduces the peak temperature by only 2 to 3 degrees — not enough to make the interior safe for any living thing.

Young children are at particularly high risk because their bodies heat up three to five times faster than an adult's. A child's core temperature can rise to a fatal level — 107°F — in as little as 15 to 30 minutes in a hot car. The most common scenario is not malicious neglect. It is a change in routine: a parent who normally drops the child at daycare forgets when a routine changes, and the child falls asleep in the back seat.

If you see a child alone in a hot car: Call 911 immediately. Stay at the vehicle. If the child is unresponsive or appears to be in distress, every state has laws protecting bystanders who break a window to rescue a child in danger. The time to wait for authorities is not when a child's life is at risk.

The same principles apply to pets. Dogs and cats cannot sweat effectively. A pet left in a parked car on a warm day can die of heatstroke in minutes. "Running into the store for two minutes" is how most pet hot-car deaths start.

The prescription list is also a heat risk list

CDC identifies several medication classes that impair the body's ability to cool itself. This is not a rare interaction affecting a small number of people. These medications are among the most commonly prescribed in the United States.

Diuretics (furosemide, hydrochlorothiazide, chlorthalidone): Reduce the body's fluid reserves. Sweating depends on adequate hydration. A diuretic-dependent person arrives at a heat event already at a fluid disadvantage.

Beta-blockers (metoprolol, atenolol, carvedilol): Limit the heart's ability to increase its output in response to heat stress. In extreme heat, the cardiovascular system must work harder to move warm blood to the skin for cooling. Beta-blockers constrain this response.

Anticholinergics (some bladder medications, antihistamines, certain antidepressants): Directly impair sweating. Some of these are available over the counter. Older adults who take a Benadryl for allergies during a heat wave may be impairing their primary cooling mechanism.

Antipsychotics (haloperidol, clozapine, olanzapine): Impair temperature regulation through multiple mechanisms. People with serious mental illness are consistently overrepresented in heat wave mortality data.

The action is not to stop these medications. It is to recognize the elevated risk and act earlier: seek air conditioning sooner, drink more water, and monitor the person more closely during heat events.

Why day three kills more people than day one

The human body is designed to recover from heat stress during cooler nighttime temperatures. Sleep in a cool environment allows core temperature to drop, hormonal systems to reset, and cardiovascular stress to ease. A single hot day is manageable for most healthy adults.

Multi-day heat waves break this recovery cycle. When overnight low temperatures stay above 80°F, the body cannot fully recover before the next day's heat begins. Cumulative physiological stress builds. By the third or fourth consecutive night without recovery sleep, even healthy adults begin to show signs of heat stress. For elderly adults and people with chronic conditions, the threshold is lower and the risk arrives sooner.

CDC's heat wave guidance reflects this: mortality rates spike on the third and fourth days of a heat event, not the first. This is why a heat wave forecast should prompt action on day one, not day three. The household that sets up a cooling plan, arranges welfare checks for vulnerable neighbors, and identifies a cooling center location on day one has options. The household that waits until someone is symptomatic on day three may not.

The overnight low is a decision trigger. When nighttime temperatures are forecast to stay above 75 to 80°F for more than two consecutive nights, treat the event as a multi-day emergency requiring active management, not passive waiting.

When the home is no longer safe

CDC's guidance is direct: air conditioning is the number one protective factor against heat-related illness and death. When a home's cooling fails or was never present, and a heat event is severe, the right action is to leave.

Public cooling centers are typically located in libraries, community centers, malls, and emergency management facilities. Most cities publish cooling center locations during heat emergencies through local emergency management websites, 211 hotlines, and local news. The time to find this information is before a heat emergency, not during one.

For households with elderly members, people with chronic conditions, or infants, the threshold for relocating to an air-conditioned environment is lower than for healthy adults. When indoor temperatures exceed 90°F and cannot be meaningfully reduced, and vulnerable people are present, the decision to relocate should already have been made.

Practical options beyond public cooling centers: a friend's or family member's home with working AC, a hotel, a hospital waiting room, a grocery store, a movie theater. The goal is sustained cool air, not any specific facility. Any air-conditioned space where someone can sit safely for several hours is a cooling resource.