Heat waves: what they are, causes and consequences

According to the World Health Organization (WHO) and the World Meteorological Organization (WMO), there is no agreed upon, single and precise definition for the “heat wave” phenomenon. However, it can be understood as a prolonged period of extremely hot, dry or humid weather, occurring day or night and beginning and ending abruptly, lasting at least two or three days. It can also be defined as an extreme climatic event with high temperatures that persist for several days in a specific geographical location.

Heat waves not only imply a considerable increase in temperature, but also bring with them a series of health and economic problems for societies.

Reports by experts from the Intergovernmental Panel on Climate Change (IPCC) have shown that in the last 50 years the frequency of heat waves has increased considerably. This problem is not a mere coincidence, since climate change is contributing to the intensification and periodicity of heat waves around the world.

You may be interested in reading this other article about Why it is hotter in coastal areas.

Heat waves do not affect everyone equally, and their impact varies depending on their intensity.

• Low intensity heat waves: these are the most common, especially during the summer months. Although temperatures are high, most healthy people can tolerate them without major problems if they take basic protective measures, such as staying hydrated and avoiding direct exposure to the sun during the hottest hours.
• Severe heat waves: These are less frequent, but pose a greater challenge, especially for vulnerable groups. Temperatures reach higher levels for several days in a row, and the accumulated heat can aggravate chronic illnesses or cause exhaustion.
• Extreme heat waves: They are rare, but very dangerous. They are characterized by extremely high and persistent temperatures, often accompanied by hot nights that prevent rest. Even young, healthy people can be affected if they do not take precautions. Additionally, the risk is multiplied for those who work or exercise outdoors.

Although heat waves are becoming more relevant today, this does not mean that they did not exist in the past. These extreme events could have gone unnoticed because they occurred in very little-known regions with few inhabitants and where records have been scarce or non-existent.

According to numerous studies, the year 2021 was characterized by the occurrence of episodes of extreme weather and climate phenomena. Events such as heat waves and droughts became relevant in different regions of the globe.

The presence of extreme temperatures is associated with the increase in the average temperature of the planet. The average annual temperatures recorded were above normal in most parts of the world, except for regions such as Alaska or Siberia. Heat waves in Europe, North Africa, South Asia and South America have exhibited anomalous temperature values ​​in 2021.

• In Europe there were thirteen daily high temperature records, making it the ninth warmest year with temperatures ever recorded. In 2017, heat waves in Spain caused extreme temperatures and thermometers read 47.2 °C in the city of Córdoba.
• In June 2021, a heat wave hit North America for its seventh warmest year on record. In Canada, the town of Lytton broke a national temperature record of 49.6°C.
• 2021 was the sixth warmest year ever recorded in South America. Argentina, during the summer of 2023, suffered one of its harshest summers in which extreme heat extended from February 28 to March 20 of that year, reaching almost 41 °C.
• The year 2021 tied 2019 as the third warmest year on record in Africa and Asia had the seventh warmest year on record.

Why is it so hot? Heat waves can be due to various causes of natural and anthropogenic origin, including:

Natural variations

The descent of dry air that heats up and invades certain regions, the greater solar radiation due to the absence of cloud cover, and the entry of hot and humid air and the absence of winds, among other factors, can be the cause of a heat wave.

Climate change

The increase in temperature due to global warming generated by a higher percentage of greenhouse gas emissions is intensifying the frequency and presence of heat waves around the world. Here you can read about the Causes and consequences of climate change and the Effects of climate change.

Urbanization

Urbanization and changes in land use can increase temperatures in cities, generating “urban heat islands” in which asphalt-based buildings accumulate a large amount of heat during the day, causing temperatures to rise.

Change in land use patterns

Changing land use patterns, such as deforestation, desertification, and the entire transformation of natural ecosystems to crop or livestock land, can contribute to the formation of heat waves by altering the reflectivity and absorption patterns of the Earth’s surface.

• Increase in vector-borne diseases: The warmer climate will increase the reproduction and distribution of vector-borne diseases.
• Greater mortality in risk groups: children, the elderly and people with risk pathologies will be more exposed to these extreme climate phenomena, which can increase the number of deaths.
• Decreased work capacity: risk of heat exhaustion, cardiac arrest, and more frequent workplace accidents for those who work outdoors.
• Decrease in agricultural production: due to the drop in food production and less access to them. The increase in temperature and the absence of precipitation reduce agricultural production.
• Energy collapse: the use of air conditioners and fans generated a considerable increase in the demand for electricity related to high temperatures, producing greater energy demand
• Risks of forest fires: due to drought due to the lack of precipitation and extreme heat, ecosystems present a high risk of fires. Here you can learn how to prevent forest fires.
• Risks to biodiversity: high temperatures can affect the survival and increase mortality levels of animal and plant species.

• Avoid exposure to the sun, especially during critical hours (10 a.m. to 4 p.m.). It is advisable to wear a hat and sunscreen at all times.
• Drink water more frequently, even when you don’t feel thirsty.
• Avoid drinks with caffeine or excessive sugar.
• Incorporate fruits and vegetables into your diet and avoid abundant and heavy meals.
• Avoid intense physical activity.
• Wear loose, light, light-colored clothing.
• Stay in well-ventilated or air-conditioned places as much as possible (either at home or in public places).
• Pay attention to warning signs, such as: intense thirst and dryness in the mouth and skin, temperature above 39ºC, excessive sweating, feeling of suffocating heat, exhaustion, dizziness or decompensation, stomach pains, lack of appetite, nausea or vomiting, headaches, among other symptoms.

Now that you know more about heat waves, we recommend reading our articles on Plants that Absorb Heat and How to Cool Your House Without Air Conditioning.

If you want to read more articles similar to Heat waves: what they are, causes and consequences, we recommend that you enter our Other environment category.