Heat Wave
Overview
A heat wave (폭염, heat wave) refers to a meteorological phenomenon in which high temperatures significantly exceeding the average temperature persist for a certain period. Due to climate change, the frequency, intensity, and duration of heat waves are increasing globally, causing health damage such as heatstroke, dehydration, and cardiovascular diseases, as well as enormous losses across society including agriculture, energy, and transportation. In South Korea, the Korea Meteorological Administration issues a heat wave advisory when the daily maximum temperature is expected to be 33°C or higher for two or more consecutive days, and a heat wave warning when it is expected to be 35°C or higher for two or more consecutive days.
Main Content
Definition and Criteria of Heat Waves
The definition of a heat wave varies by country and organization. The World Meteorological Organization (WMO) defines it as a condition where the daily maximum temperature is 5°C or more above the average maximum temperature for five or more consecutive days. The U.S. National Weather Service considers it when hot and humid conditions persist for at least two days. In Europe, criteria differ by region: in Northern Europe, temperatures of 25°C or higher for three or more days constitute a heat wave, while in Southern Europe, it is 30°C or higher. In South Korea, a heat wave special advisory is issued when temperatures of 33°C or higher persist for two or more days.
Causes of Heat Waves
The main causes of heat waves are as follows:
- Climate Change: Rising global average temperatures lead to more frequent extreme heat events. Increased greenhouse gas emissions trap heat in the atmosphere, intensifying heat waves.
- Atmospheric Circulation Patterns: Stagnant high-pressure systems create descending air currents that accumulate heat at the surface. In particular, the heat dome phenomenon makes large areas hot.
- Urban Heat Island Effect: Asphalt, concrete, and buildings absorb and re-emit solar heat, raising urban temperatures by 2–5°C compared to surrounding areas.
- El Niño and La Niña: El Niño raises sea surface temperatures in the equatorial Pacific, increasing global temperatures and the likelihood of heat waves.
Impacts of Heat Waves
Health Damage
- Heatstroke: The body's temperature regulation center fails, causing body temperature to rise above 40°C, leading to consciousness disorders and multiple organ failure. Mortality rates range from 10% to 50%.
- Heat Exhaustion: Excessive sweating depletes water and salt, causing dizziness, vomiting, and fainting.
- Heat Cramps: Occur during heavy muscle work, especially causing pain in the legs and abdomen.
- Worsening of Chronic Diseases: Symptoms of cardiovascular diseases, respiratory diseases, and diabetes worsen, increasing the risk of death.
- Mental Health: Heat waves are associated with increased anxiety, depression, and aggression, and are linked to higher suicide rates.
Social and Economic Damage
- Agriculture: Reduced crop growth, sunburn damage, and livestock deaths lead to decreased production. Particularly damaging to rice, fruit trees, and vegetables.
- Energy: Surging demand for cooling pushes electricity consumption to peak levels, increasing the risk of blackouts.
- Transportation: Damage to transportation infrastructure, including rail deformation, melting of road asphalt, and restrictions on aircraft takeoffs and landings.
- Water Resources: Linked to droughts, causing shortages of drinking water, agricultural water, and deterioration of water quality.
- Ecosystems: Increased risk of wildfires, coral bleaching due to marine heatwaves, fish die-offs, and reduced biodiversity.
Heat Wave Response Methods
Individual Level
- Hydration: Drink water regularly even without feeling thirsty. Avoid caffeine and alcohol.
- Limit Outdoor Activities: Refrain from outdoor activities between 12:00 PM and 5:00 PM.
- Maintain a Cool Environment: Use fans and air conditioners, and stay in shaded, well-ventilated areas.
- Light Clothing: Wear light-colored, loose cotton clothing, and use hats and sunglasses.
- Protect Vulnerable Groups: Special attention is needed for the elderly, infants, people with chronic diseases, and outdoor workers.
Social and Policy Level
- Heat Wave Special Advisory System: Advance preparation based on the Korea Meteorological Administration's forecasts and warnings.
- Operation of Cooling Shelters: Open air-conditioned facilities such as senior centers, community centers, and subway stations.
- Cooling Cost Support: Provide electricity bill discounts or cooling equipment support to low-income households and elderly households.
- Urban Planning: Expand green spaces, implement rooftop greening, use heat-reflective paints, and create wind corridors to mitigate the urban heat island effect.
- Agricultural Support: Develop heat-resistant crops, expand irrigation facilities, and strengthen crop disaster insurance.
Latest Trends
2024 and 2025 are considered years of record-breaking heat waves globally. 2024 was the first year the global average temperature exceeded 1.5°C above pre-industrial levels, and in India, heat waves exceeding 50°C killed hundreds. In Europe, several countries recorded their highest-ever temperatures in July 2024, and Mediterranean countries suffered from wildfires and droughts. In South Korea, the summer of 2024 saw the longest streak of tropical nights on record, with Seoul experiencing 39 consecutive tropical nights. This trend continued into 2025, with early heat observed as heat wave advisories were issued in southern regions from early May. Climate scientists predict that heat waves will become more frequent and intense, emphasizing the importance of achieving carbon neutrality goals and adaptation policies. Recently, AI-based heat wave prediction models have been developed with improved accuracy, and smart city technologies are expanding real-time temperature monitoring and alert services for vulnerable groups.
Related Topics
- [[Climate Change]]
- [[Heatstroke]]
- [[Urban Heat Island Effect]]
- [[Greenhouse Gas]]
- [[Drought]]
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