Seoul experiences record-breaking ‘tropical nights’ for 26 consecutive days. What are they and how do they affect your health?

South Korea’s capital city, Seoul, recently shattered a 118-year-old record by experiencing 26 consecutive tropical nights with overnight temperatures above 25 degrees Celsius.

This heat streak, described as unprecedented by meteorologists, is not just a weather anomaly but a growing sign of climate shifts impacting many regions globally. The effects of such prolonged heat don’t disappear with the setting sun, as nighttime temperatures fail to offer the body a respite from the intense conditions.

Youn Ki-han, director at Seoul’s Meteorology Forecast Division, told AFP, “The cold air is not coming down from the north and as we are affected by the warmer side of the southwest, the temperature is continuously recording around 25 degrees Celsius or above.”

Tropical nights are not merely a weather term — they profoundly affect our health, sleep patterns, and overall well-being. Understanding how this persistent heat affects the body is crucial for adapting to the increasing frequency of extreme weather events as global temperatures continue to rise.

Dr Siva Karthik Reddy, MBBS, MD, general medicine, says, “The respite of cool nights allows our bodies to recover and reset. However, with the increasing frequency of tropical nights—where temperatures remain above 20 degrees Celsius (68 degrees Fahrenheit)—this essential cooldown period is being disrupted, leading to a cascade of physiological and health consequences.”

Impact on the body’s ability to recover and regulate temperature

Dr Reddy tells indianexpress.com, “Our bodies rely on a delicate balance of heat production and heat loss to maintain a stable internal temperature. During sleep, our core body temperature naturally drops, facilitating various restorative processes. However, when nighttime temperatures remain high, our bodies struggle to dissipate heat effectively, impacting both recovery and overall well-being.”

The body’s primary cooling mechanism, sweating, becomes less efficient in humid conditions, as the air is already saturated with moisture. This can lead to heat stress, where the body struggles to maintain a safe temperature, says Dr Reddy.

He adds that the elevated core body temperature can disrupt sleep patterns, making it difficult to fall asleep and stay asleep. This can lead to sleep deprivation, impacting cognitive function, mood, and overall health.

To compensate for the impaired heat dissipation, the heart works harder to pump blood to the skin for cooling. This can lead to an increased heart rate and elevated blood pressure, putting additional strain on the cardiovascular system.

Sleep deprivation and heat stress can negatively impact cognitive function, affecting memory, concentration, and decision-making abilities (Source: Freepik)

Impact on overall health

Dr Reddy says, “Repeated exposure to tropical nights can have far-reaching consequences for human health, beyond just sleep deprivation. The inability to adequately cool down at night can lead to chronic stress on the body, increasing the risk of developing or exacerbating conditions like anxiety and depression.”

The persistent elevation in heart rate and blood pressure associated with tropical nights can put a significant burden on the cardiovascular system, potentially increasing the risk of heart disease, stroke, and other cardiovascular complications.

Sleep deprivation and heat stress can negatively impact cognitive function, affecting memory, concentration, and decision-making abilities, states Dr Reddy. The combined effects of sleep deprivation, fatigue, and cognitive impairment can lead to decreased work productivity and increased risk of accidents.

The elderly, young children and those with pre-existing health conditions are particularly vulnerable to the adverse effects of tropical nights.

Climate change and the rise of tropical nights

Dr Reddy cautions, “The increasing frequency of tropical nights is closely linked to broader climate patterns. Rising global temperatures, driven by greenhouse gas emissions, are causing warmer nights and more frequent heatwaves. Urban areas are particularly susceptible to the ‘urban heat island effect,’ where concrete and buildings trap heat, leading to even higher nighttime temperatures.”

As climate change continues to accelerate, we can expect to see an increase in the number and intensity of tropical nights, which will pose significant challenges to human health and well-being.

Adapting to tropical nights: Lifestyle and health adjustments

While we work to address the root causes of climate change, individuals can take steps to mitigate the impact of tropical nights on their health:

Optimise sleep environment: Keep your bedroom cool and well-ventilated. Use fans, air conditioning if available, and breathable bedding.

Hydration and electrolyte balance: Stay well-hydrated throughout the day and consider consuming electrolyte-rich drinks to replenish lost minerals from sweating.

Light clothing and bedding: Wear loose-fitting, lightweight clothing and opt for breathable bedding materials like cotton or linen.

Cool showers before bed: A cool shower before bed can help lower your body temperature and promote relaxation.

Limit alcohol and caffeine: These substances can interfere with sleep and contribute to dehydration.

Check on vulnerable people: During heatwaves, regularly check on elderly family members, neighbours, or those with health conditions.

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