The hidden dangers of heat waves

FILE - In this Thursday, July 1, 2021 file photo, a farmworker wipes sweat from his neck while working in St. Paul, Ore., as a heat wave bakes the Pacific Northwest in record-high temperatures. As outlandish as the killer heat wave that struck the Pacific Northwest and other areas was, it fit into a decades-long pattern of uneven summer warming in the United States, climate scientists say and federal weather records show. (AP Photo/Nathan Howard, File)

The main danger with a heat wave is probably obvious: too much time spent in the heat can quickly lead to illnesses such as heat exhaustion or heat stroke, which could prove fatal. But in the rush to avoid those dangers, many hidden perils can cause just as many troubles as the heat's direct effects on the body.

A stretch of warm weather officially becomes a heat wave when a location faces two or more days of temperatures higher than the historical averages for that area. Those standards can change depending on the region, as a stretch of triple-digit temperature days in June may be average for Death Valley, but the same temperatures farther north might shatter all-time records.

But the numbers on the thermometers may not matter as much as the acclimatization of local residents, where many hidden dangers camouflage themselves. Southern California residents may be accustomed to the heat and have the air conditioners ready to go, but a Seattle native who has never experienced similar temperatures could be in a world of trouble.

Heat is the most deadly weather-related killer in the United States, and hyperthermia and dehydration aren't always the main culprits.

From the dangers of cooling down too quickly to the troubles of what you may run (or swim) into while cooling down, the AccuWeather news team compiled a few of the hidden dangers you may not expect from a heat wave.

You've been stuck outside in the sweltering heat and the dreaminess of taking a freezing cold shower or taking a dip in a frigid stream may seem irresistible, right? Wrong.

Cold shock can kill.

"Fifty-five-degree water may not sound very cold, but it can be deadly," the National Weather Service warns.

While warm outside air may trick you into thinking that local bodies of water are also warm, a sudden cold plunge can shock your brain and cause dramatic changes to your breathing, heart rate and blood pressure.

A young visitors covers his nose as he submerges under water to cool as temperatures rise at Castaic Lake Thursday, July 8, 2021, in Castaic, Calif. (AP Photo/Marcio Jose Sanchez)

"Cold water drains body heat up to 4 times faster than cold air," the NWS cautions. "The sudden gasp and rapid breathing alone creates a greater risk of drowning even for confident swimmers in calm waters. In rougher open water this danger increases."

Keith Bills, course manager at the National Ice Rescue School for the Coast Guard, explained to AccuWeather that cold shock can even trigger a gasp reflex that can cause you to uncontrollably inhale water when you go under. Such a reflex may be fatal.


Even after the initial shock, the second phase of cold water immersion can prove fatal.

Once water temperatures slip under 77 degrees Fahrenheit, Bills said the human body will begin to naturally preserve its vital organs by decreasing blood flow to the arms and legs, making swimming even more difficult.

This type of short-term immersion causes "the loss of performance where you get cold muscle tissue and you lose the ability to even swim, move your arms or even hold onto anything," he said.

Patrons of the Bitterroot River jump into the cool water as temperatures crested 100 degrees in Missoula, Montana, on Wednesday, June 30, 2021. (AP Photo/Tommy Martino)

While death by drowning is a tragedy that can occur during any time of the year, hospitalizations related to non-fatal drownings have spiked during heat waves, and can be directly related to people spending more time than usual in the water to cool off.

Non-fatal drowning incidents can be more common during heat waves because of that rush to cool down, leading more inexperienced swimmers and children into the water.

According to data released by the Oregon Health Authority during the state's record-breaking heat wave of June 2021, hospitalization queries for non-fatal drowning or submersion cases were abnormally high on June 27 to June 29.

During that three-day period, a stretch of record-breaking heat took hold, culminating with a high of 116 degrees. This is mind-boggling weather for a city that averages high temperatures in the upper 70s at that time of year and a new all-time high for Portland.

According to Royal Life Saving, people who survive a drowning incident often experience lifelong health issues, which in some cases, may lead to premature death. Damage to organs, including the brain, can range from mild to moderate to severe in cases of non-fatal drowning.

During that same Oregon heat wave, data from the health authority also showed a sharp spike in hospital visits for reasons related to exposure to cyanobacteria. According to the Centers for Disease Control and Prevention (CDC), cyanobacteria, or blue-green algae, which live in bodies of water and multiply quickly when in the right environment of sunlight and warmth.

A fisherman in a rubber boat is surrounded by rotting cyanobacteria in the Kyiv Water Reservoir near Kyiv, Ukraine, Sunday, Nov. 15, 2020. The region was rocked by extreme hot weather throughout 2020 that resulted in widespread damage to agricultural crops and destruction to the natural habitat of some species. (AP Photo/Efrem Lukatsky)

"Blooms can form in warm, slow-moving waters that are rich in nutrients from sources such as fertilizer runoff or septic tank overflows," the CDC wrote.

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During the Oregon heat wave, the cyanobacteria began blooming at the same time as residents began jumping in lakes to escape the heat wave. As a result, hospitalization rates for bacteria exposure spiked during that final week of June,

"Exposure to cyanobacteria can result in symptoms including skin rash, diarrhea, cramps, vomiting, numbness, and fainting," the health authority said.

Yes, dehydration is overhydration's far more sinister sibling, but the dangers of overhydration are often unrecognized and under-addressed.

The danger from drinking too much water comes when the sodium counts in your body begin to become diluted. This triggers hyponatremia, a condition that essentially drowns the own body internally.

A man drinks a bottle of water in the heat during a Juneteenth commemoration at Leimert Park Plaza on Saturday, June 19, 2021, in Los Angeles. (AP Photo/Ringo H.W. Chiu)

"The primary issue of having too much water is you drown in your own water a little bit, it dilutes your sodium in your blood and your biggest risk is that it can cause a change in the way your brain works," Dr. Matthew McElroy, a sports medicine specialist and primary care doctor with Geisinger Health Systems in Pennsylvania, told AccuWeather.

Hyponatremia often announces its arrival with symptoms including headaches, nausea, drowsiness, muscle weakness and seizures.

According to a publication from researchers at Linköping University in Sweden, heat waves appear to increase the prevalence of hyponatremia, particularly among users of medical drugs that heighten patients water retention. When those patients consume more water during heat waves to cool themselves down, they subsequently increase their odds of diluting the sodium in their bodies.

"Warm weather increases the risk of drug-induced hyponatremia," read the study's conclusion. "Increased awareness of risk drugs and adjustment of medication use by patients with a high risk of drug-induced hyponatremia could potentially prevent this condition."