Tropical Night
Overview
A tropical night (열대야, tropical night) refers to a night when the minimum temperature of the day is 25°C or higher. It mainly occurs in summer under hot and humid climatic conditions. Tropical nights impair the body's thermoregulation ability, leading to various health issues such as sleep disorders, heatstroke, and worsening cardiovascular diseases. Recently, due to global warming, the frequency and intensity of tropical nights are increasing worldwide.
Main Content
Definition and Criteria
Meteorologically, a tropical night is defined as a case where the minimum temperature between 6 PM and 9 AM the next day is 25°C or higher. This criterion varies by country; for example, the Japan Meteorological Agency uses 25°C, while some European countries use 20°C. The Korea Meteorological Administration has officially observed tropical nights since 1973.
Causes
Tropical nights occur due to a combination of factors. First, solar radiation accumulates on the ground surface and is not sufficiently released at night. Second, high humidity prevents sweat evaporation, raising the perceived temperature. Third, the urban heat island effect keeps city centers 2–5°C warmer than suburbs. Fourth, rising average temperatures due to climate change increase the likelihood of tropical nights.
Health Impacts
Tropical nights have various negative effects on the human body. Sleep disorders are the most common, disrupting deep sleep and leading to fatigue and reduced concentration the next day. Prolonged periods can weaken immunity, raise blood pressure, and increase heart strain. The elderly, those with chronic diseases, and infants are particularly at high risk of heatstroke or heat exhaustion and require special caution. Studies also show that emergency room visits increase by 20–30% during tropical night periods compared to normal times.
Socioeconomic Impacts
Tropical nights affect society broadly. Electricity consumption surges as cooling demand peaks, potentially causing blackouts or power shortages. In agriculture, livestock stress increases, reducing productivity, and incidents of fish and shellfish die-offs occur. Additionally, increased nighttime activity is reported to temporarily raise crime rates. Economic losses are estimated to reach hundreds of billions of won annually.
Countermeasures and Adaptation Strategies
Various measures are being implemented to reduce damage from tropical nights. At the individual level, using fans or air conditioners, taking lukewarm showers, using thin blankets, and maintaining bedroom temperatures at 26–28°C are recommended. At the community level, cooling centers, expanded heat shelters, and visiting health management services for vulnerable groups are provided. Long-term strategies include expanding urban green spaces, rooftop greening, using high-reflectivity building materials, and implementing heat island mitigation policies.
Historical Cases
The most severe tropical nights in South Korea occurred in the summer of 2018, with 39 consecutive tropical nights recorded in Seoul—the longest since meteorological observations began in 1907. In 1994, severe tropical nights from July to August caused many deaths. In Japan, Tokyo observed 15 consecutive tropical nights in 2023, and in Europe, record-breaking tropical nights occurred alongside a heatwave in 2022.
Latest Trends
In 2024 and 2025, as the global average temperature exceeded 1.5°C above pre-industrial levels, the frequency of tropical nights has surged worldwide. The Korea Meteorological Administration announced that the number of tropical night days in summer 2024 more than doubled compared to the average (1973–2020). Particularly, Jeju Island and the southern coastal areas experienced over 20 tropical night days in July alone. According to climate model predictions, by 2050, the annual number of tropical night days in Seoul is expected to triple the current level. Consequently, governments are incorporating tropical nights into disaster management systems and strengthening adaptation policies. Real-time thermal environment monitoring systems using smart city technology, AI-based tropical night prediction models, and personalized health alert services are being introduced. Additionally, legislation mandating enhanced building insulation and heat island mitigation designs in urban planning is being pursued.
Related Topics
- [[Heatwave]]
- [[Climate change]]
- [[Urban heat island]]
- [[Sleep disorder]]
- [[Heat-related illness]]
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