Extreme Temperature Safety: Heat- and Cold-Related Illness

Venturing outdoors means needing to be prepared for all sorts of weather — rainy days, dry days, and from the hottest daytime hours to the coldest nights.

The hypothalamus, in the lower middle part of your brain, helps keep your internal temperature steady throughout the day. In this process, called thermoregulation, the hypothalamus communicates with temperature sensors in your skin and organs and then activates certain mechanisms to warm or cool the body.

Although your hypothalamus can adapt to a wide range of temperatures, its task is easiest when the air around you is 20ºC to 25ºC (68ºF to 77ºF). When it’s cooler, you can usually bundle up in more layers. When it’s warmer, you might use fans or air conditioners to maintain a healthy core temperature.

In some cases, you may find yourself in an environment with extreme temperatures, and your hypothalamus may not be able to compensate quickly enough.

It’s crucial to know what health concerns you may face and how to avoid any temperature-related health problems.

Even when environmental temperatures rise to 130ºF (54ºC), your body can maintain its core internal temperature. But temperatures can be dangerous to your body well before they get this high.

The National Weather Service notes that prolonged time or physical activity outdoors with a heat index of 80ºF (27ºC) or higher could cause fatigue and warrants caution.

At a heat index of 90ºF (32ºC), there is a risk of:

This risk is much higher at a heat index of 103ºF (39ºC), with heatstroke likely at 125ºF (52ºC).

Other heat-related illnesses include:

Some common symptoms of heat exhaustion include:

• sweating heavily
• exhaustion or fatigue
• dizziness or lightheadedness
• blacking out or feeling dizzy when standing up
• weak but fast pulse
• nausea
• vomiting

Symptoms of heatstroke include:

• discolored skin that feels hot to the touch
• strong and fast pulse
• losing consciousness
• internal body temperature of 104ºF (40ºC) or higher

If someone loses consciousness and shows one or more of the symptoms of heat exhaustion or heatstroke, call 911 or your local emergency services right away.

To treat heat exhaustion, try to keep yourself cool with cold, damp cloths around your body and slowly take small sips of water until the symptoms begin to fade. Try to get out of the heat. Find a place with air conditioning or a lower temperature (especially out of direct sunlight). Rest on a couch or bed.

To treat heatstroke, cover yourself with cold, damp cloths or take a cold bath to normalize your body temperature. Get out of the heat immediately and go to a place with a lower temperature. Don’t drink anything until you (or the person experiencing heatstroke) receive medical attention.

Staying well-hydrated is one of the best ways to avoid heat-related illness. Drink enough fluids so that your urine is light-colored or clear. Don’t rely solely on thirst to guide how much liquid you should drink. When you lose a lot of fluids or sweat profusely, be sure to replace electrolytes as well.

Wear clothing that is appropriate to your environment. Clothes that are too thick or too warm can quickly cause you to become overheated. If you feel yourself getting too hot, loosen your clothing or remove excess clothing until you feel cool enough.

Wear sunscreen when possible to avoid sunburn, which makes it harder for your body to get rid of excess heat.

Try to avoid places that can get extremely hot, such as inside cars. Never leave another person, child, or pet, even for short periods.

As with high temperatures, don’t rely solely on the thermometer reading of environmental air for gauging cold temperatures. The wind speed and external body moisture can cause a chill that dramatically changes your body’s rate of cooling and how you feel.

In extremely cold weather, especially with a high wind chill factor, you can quickly experience the onset of hypothermia, a body temperature below 95ºF (35ºC). Falling into cold water can also result in immersion hypothermia.

Your ability to regulate your temperature weakens the more your internal body temperature decreases. If your body temperature reaches 85ºF (29.4ºC), the hypothalamus loses its ability to regulate your body temperature.

At air temperatures below 5ºF (-15ºC), you’re more likely to develop frostbite, a type of skin damage due to extreme cold.

But the temperature doesn’t need to drop that much for cold injuries to occur. Nonfreezing cold injuries, such as trench foot (aka immersion foot) and chilblains (aka pernio), can develop at temperatures of 0ºC to 10ºC.

When your body temperature first drops, you’ll start to shiver as your body tries to increase your body temperature. Shivering alone can quintuple your heat production. Your heart rate may also increase for this reason.

When your body temperature is between 90ºC and 95ºC (32ºC and 35ºC), you may experience:

• hunger
• pale, dry skin
• nausea
• fatigue
• unclear speech
• memory loss
• rapid breathing
• high blood pressure
• an increased urge to urinate

Between 82ºC and 85ºF (28ºC and 32ºC), you’ll likely stop shivering but experience other symptoms, such as:

A body temperature below 82ºF (28ºC) can result in:

It may ultimately lead to death. About 700 to 1500 people die of hypothermia in the United States each year.

If someone passes out, shows multiple symptoms listed previously, and has a body temperature of 95ºF (35ºC) or lower, call 911 or your local emergency services immediately. Perform CPR if the person isn’t breathing or doesn’t have a pulse.

To treat hypothermia, get out of the cold as soon as possible and to a warmer environment. Remove any damp or wet clothing and start warming up the middle areas of your body, including your head, neck, and chest, with a heating pad or against the skin of someone with a normal body temperature.

Drink something warm to increase your body temperature gradually, but don’t drink anything with alcohol.

Even after you begin to feel warm again, stay dry and wrap yourself in a warm blanket. Seek medical help right away to minimize the harm to your body.

To treat frostbite, soak and swirl the affected area in warm water at 98.6ºF to 102.2ºF (37ºC to 39ºC) until it turns red or purple. Keep any toes or fingers affected by frostbite separated to avoid rubbing the areas against each other. Do not rub, use, or walk on frostbitten skin, as this can cause tissue damage.

See a doctor if you still can’t feel anything on your frostbitten skin after 30 minutes.

The human body is designed to handle considerable shifts in external temperature. However, most of us experience temperatures well beyond even this range. Extreme heat or cold can cause significant damage to our internal systems, even resulting in death.

As climate change threatens to bring more extreme temperatures in the decades to come, the potential global health impact may be profound.

But on an individual level, we can begin to help protect ourselves and others from serious harm by recognizing the effects of extreme temperatures. We can also take preventive measures, encourage others to do the same, and advocate for those in our community who need our support.