These 6 Health Risks Can Significantly Increase on Hot Days

• Temperatures are rising across the U.S. (and the globe) as summer and climate change take hold.
• Research indicates that heat can raise the risk of all-course mortality.
• Specifically, doctors and data point to certain health risks that increase along with temperatures, including migraine episodes, heart attacks, and strokes.

While heat and summer go hand in hand, research and experts indicate that rising temperatures and health risks do, too.

One 2022 study of more than 219 million U.S. adults ages 20 and older suggested a link between extreme heat and all-course mortality. The most significant risks were to older individuals. However, health experts say it’s critical for everyone to understand the health risks that can come with extreme heat.

“It is easy in the summer to be distracted by lots of fun outdoor activities, but heat can impact your health and make you very ill, especially if you are not paying attention to signs from your body or are at extremes of age,” says Dr. Jo Anna Leuck , MD, the associate dean of educational affairs at Burnett School of Medicine at Texas Christian University. “There are easy ways to prevent this impact, so it is important to understand the dangers of heat and how to avoid them.”

This awareness is especially critical as the planet warms due to climate change. According to the National Oceanic and Atmospheric Administration (NOAA), 2023 was the warmest year on record.

Early indications are that 2024 will follow suit. April was the warmest month on record, marking the 11th straight time a month has set a new high mark.

To help you prepare for the warmer season and the years ahead, doctors shared six ways the heat can increase health risks and tips for staying cool.

6 Health Risks That Rise With Hot Weather

Christopher F. Freer, DO , the senior vice president of Emergency and Hospitalist Medicine at RWJBarnabas Health in New Jersey, explains that specific populations are at higher risk of experiencing health issues in hot weather.

These populations include:

• Infants and young children whose bodies can’t regulate temperature as well or request/access fluids on their own
• Older adults, particularly those with underlying conditions
• Pregnant people
• People with chronic health conditions

Still, no one is immune to heat-related health issues, and understanding the signs can help you protect yourself (and anyone around you who may be at a higher risk for more severe outcomes).

The following are six of the most common health risks that can increase when temperatures are higher.

Migraine attacks

Data indicates that migraine attacks affect 12 to 15% of the general population. The effects can be debilitating.

“Migraines are not ‘bad headaches,’” says Dr. Joshua Feinstein, MD, an emergency medicine physician at Memorial Hermann .

While throbbing headaches are one symptom, others include:

• Light and sound sensitivity
• Irritability
• Cravings
• Seeing odd shapes or hearing things an hour before a migraine (aura)
• Nausea
• Dizziness

Recent research suggests that heat might raise the risk of an attack. For instance, an observational study based on daily diary records of 660 migraine patients presented at the 66th Annual Scientific Meeting of the American Headache Society, held June 13-16, indicated that heat could increase migraine attack risk.

However, the findings have not yet been published in a peer-reviewed scientific journal.

A 2023 observational study of more than 40,000 respondents, including more than 15,000 people with migraine, suggested that different weather types, including high humidity, increased headache occurrences.

“Heat adds to inflammatory effects that can prolong migraines,” Feinstein says. “Furthermore, people may be dehydrated, which decreases their ability to work to fight a migraine.”

Feinstein suggests people with migraine — whether it’s exacerbated by the heat or not — work long-term with a neurologist or other healthcare professional to minimize attacks and find relief when they occur.

Heart attack

Research published in Circulation in 2023 suggested that cardiovascular disease deaths caused by heat could surge by an estimated 162% by mid-century (2036-2065).

Another 2023 Circulation study of more than 202,000 heart attack deaths in Jiangsu, a province in China, indicated a significant link between a person’s chances of dying from a heart attack and extremely hot and cold temperatures.

“When we are exposed to heat and especially temperatures higher than our body temperature, the heart has to work a lot harder and beat faster, as it needs to circulate the blood out toward the skin to allow for sweating and other mechanisms the body utilizes to protect from heat,” Leuck says. ”The increase in work can lead to heart attacks and other heart problems in those at risk.”

Feinstein says chest pain or pressure is the most common heart attack sign, but others include:

• Arm pain
• Shortness of breath
• Nausea
• Lightheadedness

“If you are experiencing these symptoms, you should immediately call 911 and get out of the heat if possible,” Feinstein says.

Stroke

One 2020 study indicated that weather conditions, including high temperatures, are becoming a novel stroke risk factor. The authors noted that there can be a lag period of one to six days between weather exposure and stroke.

Another published in the same year but has not yet been published in a peer-reviewed scientific journal, suggested that stroke severity went up by more than two-thirds (67%) for every 9°F uptick in the average temperature range over three days.

Leuck points to the same reason as heart attack risk as the primary one for the increase in stroke severity.

“Extreme heat puts stressors on the body, especially in the elderly, and this can lead to an increased incidence of stroke, especially those with other risk factors such as high blood pressure,” Leuck says.

Leuck says stroke symptoms include:

• Weakness of arms or legs, especially on one side
• Vision changes
• Facial droop
• Slurred speech
• Difficulty walking or feeling off balance

“Call 911 if you have these symptoms,” Leuck stresses. “Time is of the essence when treating a stroke.”

Heatstroke

“Heat increases the risk of stroke both through causing ‘regular’ strokes through dehydration, but also in causing Heat Stroke by elevation of body temperature,” Feinstein explains.

Like strokes, Freer says that heatstroke is a medical emergency.

“The signs of heatstroke are confusion, altered behavior, a change in speech, and even seizures,” Freer says.

Heat stroke is not the same as heat exhaustion, but the two are related.

“Heat exhaustion is your body’s warning sign that it’s overheating,” Freer says. “Symptoms like headache, dizziness, and nausea signal the need to cool down and rehydrate with fluids and electrolytes…Seek shade, rest, and apply cool compresses.”

Freer also recommends steering clear of caffeine and alcohol, which can make dehydration worse.

Worsening of kidney disease

Kidney disease affects an estimated 37 million Americans , and research published in 2022 suggested a significant association between kidney disease-related emergency room visits and extreme heat exposure.

The study is based on more than 1 million kidney disease-related emergency room visits in New York from 2005 to 2013. There was a stronger association between visits and people with acute kidney injuries, kidney stones, and urinary tract infections.

“The kidneys help our body regulate fluid, and with excessive heat, leading to excessive sweating in addition to the other stressors on the body, kidney problems can worsen,” Leuck says.

Additionally, kidneys need fluids to function, and dehydration risks are higher in the heat, Feinstein explains.

Higher or lower blood pressure

Heat can cause blood pressure to become too low or too high.

“Hot weather can trigger low blood pressure for a few reasons,” Freer says.  “When you sweat heavily, your body loses fluids and blood volume. This decrease in volume can lead to a drop in blood pressure.”

Freer says this issue can become more pronounced when changing positions, such as standing up after lying down. Dizziness and lightheadedness are symptoms associated with low blood pressure.

Freer adds that dehydration’s strain on the kidneys can also decrease blood pressure, especially in dehydrated people.

On the flip side, some people may experience increased blood pressure.

“Heat can cause higher blood pressure because the body has to work harder to circulate blood to try to keep cool and allow for sweating and evaporation that is needed so that the body temperature does not get elevated, as can happen in heat stroke,” Leuck says.

Leuck says high blood pressure can be asymptomatic but could also trigger headaches and dizziness.

How to stay safe and cool in the heat

Experts who spoke with Healthline said it’s best not to try to beat the heat but to cope with it safely. These steps include:

• Knowing your risk for heat-related health issues
• Remaining hydrated (Fluid intake depends on various factors, including age and health, pregnancy, and lactation status)
• Drinking two to three cups of water before venturing out in the heat
• Avoiding physical exertion if the “feel like” temperature is over 90 degrees
• Seeking shade and wearing protective clothing, like hats, when outdoors
• Using fans and misters
• Taking breaks in the air conditioning
• Watching for signs of illness
• Seeking medical care promptly if you are concerned

“If you’re feeling dizzy, weak, headache, or nauseous, get out of the heat, drink lots of fluids, and use a wet cloth or an ice pack,” Freer says. “If that doesn’t work, call your doctor. If you or someone you know is experiencing an altered mental status, call 911. They could be experiencing heat stroke.”

Takeaway

Heat can play a role in increased health risks, including heart attack, stroke, worsening kidney disease symptoms, blood pressure changes, and heat stroke.

People who are older, pregnant, have underlying health conditions, and young children are at a higher risk for experiencing health issues in the heat, though anyone can.

You can protect yourself and loved ones by remaining hydrated, seeking shade or air conditioning, avoiding physical exertion in sweltering temperatures, and seeking medical care if you are concerned about your health or that of a loved one.