Excessive heat warnings and heat-related illness

From the desk of
Luis Villaseñor
ScienceExcessive heat warnings and heat-related illness

Extreme heat is serious business — it’s the leading cause of weather-related deaths in the United States each year. So if you see an “excessive heat warning” pop up in your weather app, you’ll want to be prepared.

Most of this preparation seems like common sense. Ensure you have water, electrolytes, cool towels, and other helpful equipment for that day’s activities. Avoid strenuous work outdoors if possible. Keep track of loved ones, pay extra attention to your little ones, and don’t forget the pets! Stay cool and stay hydrated.

But within these common-sense rules, you’ll find confusion in unexpected places — especially when it comes to staying hydrated. Many people think that staying hydrated means chugging water like a storm drain even when you’re not thirsty.

In practice, this belief can lead to dangerous electrolyte imbalances, particularly when combined with warm-weather activities that induce a lot of sweating. Unsurprisingly, people hospitalized during a heat wave often have clinically low sodium levels due to sweat loss and overhydration.

So, hot-weather hydration plans actually need to be a bit more calculated than common sense may imply. I’ll lay out that plan in the second half of this article and share practical tips for preventing, identifying, and treating heat-related illnesses. First, we’ll cover the fundamentals of heat alerts so you understand what various alerts mean and how to be prepared.

What Is an Excessive Heat Warning?

An excessive heat warning is the most severe of the three extreme heat alerts issued by the National Weather Service. Here are those alerts, in ascending order of urgency:

  1. An excessive heat outlook warns of dangerously hot conditions in the next 3-7 days
  2. An excessive heat watch warns of dangerously hot conditions in the next 24 to 72 hours
  3. An excessive heat warning warns of dangerously hot conditions in the next 12 to 24 hours

How hot is dangerously hot? The criteria vary by county, but you’re typically looking at temperatures north of 100℉. (Keep in mind that humidity also factors in.)

Often, the National Weather Service issues a less severe “heat advisory” for 100℉ (or higher) temperatures, but don’t take any of these alerts or advisories lightly. Older folks in particular should be more careful in the heat because their bodies may have greater difficulty staying cool.

The Dangers of Hot Weather

The most direct dangers of hot weather are heat-related illnesses including heat cramps, heat exhaustion, and heatstroke. Older folks with impaired sweating and other potential thermoregulatory issues, as well as infants are especially vulnerable when it’s hot outside.

Hot weather can also cause fluid and electrolyte imbalances that affect many critical organ functions, most notably your brain. When you sweat, you lose significant water and sodium. You must replace both to keep your body functional.

Okay, so your weather provider is warning of extreme heat. How should you prepare for it?

Preparing for a Heat Wave

If heat is in the forecast, you’ll want to be prepared. These tips will help.

#1: Keep fluids and electrolytes handy

Plan to have plenty of fluids and electrolytes (like LMNT) around, but understand that sweat loss and therefore hydration needs are highly individual. Some people sweat very little, while others sweat excessively even at lower temperatures — a nuanced condition called hyperhidrosis. The more you sweat, the more sodium and fluids you need to replace.

Your hydration strategy will also depend on your outdoor plans. Are you planning on golfing, running, or hiking alongside an active volcano? Pack accordingly.

#2: Plan to stay cool

Most days, I’ll take outdoor over indoor activity. Being in nature has health benefits, plus it just feels better. But when you see a heat alert, it’s worth reconsidering. Can you move your jog to the early morning when it’s 20 degrees cooler? Do you have an air-conditioned gym nearby?

The late spring and early summer are also excellent times to ensure your air conditioning is working properly. If you don’t have A/C, consider installing it. If that’s not an option, plan to visit a place with A/C (mall, store, gym, etc.) on sweltering days.

#3: Gather supplies

Like other weather events, heat waves may occasionally affect the supply chain. Consequently, it’s wise to store 1-2 weeks of emergency supplies that require no refrigeration during a potential power outage (canned goods, bottled water, etc.). Better safe than sorry.

During an Excessive Heat Warning

When the blistering heat arrives, you’ll be glad you prepared for it. Here are some tips for managing the extreme heat when it arrives.

#1: Stay hydrated (water plus electrolytes)

To replace what’s lost through sweat, urine, and respiration, you need to:

  1. Consume adequate fluids
  2. Consume adequate electrolytes

Fluids are the easy part. When you need fluids, your hypothalamus detects low blood volume and makes you thirsty. Then you drink something, and fluid balance is restored. That’s why dehydration is rare in healthy adults.

Electrolytes are the often-neglected part. Consuming electrolytes — especially sodium — along with your water is a crucial part of staying hydrated. Many people drink oodles of plain water, then end up with cramps, fatigue, light sensitivity, lethargy, and other low sodium symptoms. This is precisely what we had in mind when we created LMNT, our tasty, zero-sugar, grab-and-go electrolyte drink mix.

#2: Stay cool

A heat wave isn’t the time to maximize outdoor efforts. Elite athletes can sometimes manage significant exertion in hot weather, but even they can succumb to heat stress, especially when drinking too much plain water.

If you find yourself overheating, get yourself out of the furnace. Grab a cool, wet towel for your neck, find some shade, sit down, and let your body cool off. Better yet, get into a climate-controlled room when possible.

#3: Stay vigilant

If you’re taking care of people or animals during extreme heat, take heed. This means:

  • Not leaving them unattended in a car
  • Checking in to ensure proper hydration
  • Ensuring they have access to A/C
  • Monitoring for signs of heat-related illness

Let’s double-click on that last bullet before we wrap things up.

Identifying and Treating Heat-Related Illness

During an excessive heat warning, look out for heat-related illnesses. The big three are:

  1. Heat cramps
  2. Heat exhaustion
  3. Heatstroke

#1: Heat cramps

Heat cramps are a subset of muscle cramps. Water and sodium losses from sweating cause these sustained, painful spasms.

Sodium plays a crucial role — salt supplementation relieved muscle cramps in 1920s industrial workers. And more recently, researchers noticed that athletes who excrete greater quantities of salt through sweat tend to cramp more frequently.

To treat heat cramps, replace sodium and fluids while resting in a cool place. For the complete treatment, check out this article on preventing heat cramps.

#2: Heat Exhaustion

Prolonged exposure to high temperatures causes a form of heat stress called heat exhaustion. Symptoms of heat exhaustion include:

  • Nausea
  • Cold or clammy skin
  • Excessive sweating
  • Tiredness
  • Dizziness
  • Headache
  • Muscle cramps
  • Fainting

To treat heat exhaustion, rest in a cool room while you rehydrate and seek medical help if the symptoms worsen. Read this article for more on preventing heat exhaustion.

#3: Heatstroke

Heatstroke is the most dire form of heat illness. When someone has heatstroke, their body temperature can exceed 104℉. The symptoms are comparable to heat exhaustion but more severe.

If you suspect heatstroke, call 911 immediately. Afterward, move the person to a cool environment and wait for help. The priority is to prevent airway obstruction, so don’t try to force rehydration if they seem close to fainting. Here’s an article dedicated to heatstroke.

Staying Safe During an Excessive Heat Warning

Preventing heat-related illness comes down to proper planning. On scorching hot days, this means:

  • Moderating (or minimizing) outdoor exercise
  • Utilizing air conditioning 
  • Hydrating with water AND electrolytes
  • Checking in on loved ones, particularly pets, children, and older folks.

By checking these boxes, we can prevent most cases of heat-related illness. Help more people stay safe by spreading the word and sharing this blog.

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