What is a heatwave?

Summer heat

During the summer the temperatures in many parts of the world are very high. This is something that we all have assumed, but sometimes the heat can get extreme and also last several days, weeks and even months.

This phenomenon is known as heat wave, and it can have very serious consequences for health and life.

What is a heatwave?

Wooden thermometer

The heat wave is a episode of abnormally high temperatures that persist for several days or weeks and that also affect a significant part of the geography of a country. How many days or weeks? The truth is that there is no "official" definition, so it is difficult to specify how many.

In Spain, it is said that it is a heat wave when extremely high temperatures are recorded (taking the period 1971-2000 as a reference) in at least 10% of the meteorological stations for at least three days. But really this threshold can vary a lot depending on the country, for example:

  • In Netherlands It is considered a heat wave when temperatures above 5ºC are recorded for at least 25 days in De Bilt, which is a municipality belonging to the province of Utrecht (Holland).
  • In United States: if temperatures above 32,2ºC are recorded for 3 days or more.

When it occurs?

Parasol on a beach in summer

The vast majority of the time occur in the canicular period, which usually occurs in summer. The Canicula It is the hottest period of the year, and it takes place between July 15 and August 15. Why are they said to be the hottest days?

We tend to think the first day of summer (June 21 in the Northern Hemisphere and December 21 in the Southern Hemisphere) is the hottest day, but this is not always the case. The planet Earth, as we know, rotates on itself, but it also tilts slightly. The day of Summer Solstice, the sun's rays reach us straighter, but since the water and the earth have only just begun to absorb heat, the temperature remains more or less stable.

Still, to As the summer progresses the ocean water, which until now refreshed the atmosphere, and the ground will have warmed up enough to start a very hot period, which can be more or less intense depending on the area in which we live. Thus, for example, in Mediterranean-type climates during the heatwave an extremely hot heat wave can occur.

What consequences can a heat wave have?

Forest fire, one of the consequences of the heat wave

Although they are natural phenomena and we have no choice but to try to adapt as best we can, if we do not take the necessary measures we could suffer their consequences, which are not few.

Forest fires

When there is a heat wave during a drought, forests are in serious danger of catching fire. In 2003, In Portugal alone, fire destroyed more than 3.010 km2 of forest.


Children, the elderly and those who are ill are the most vulnerable to heat waves. Continuing with the example of the one in 2003, more than 1000 deaths occurred during a week, and more than 10.000 in France.


When it is very hot, our mood can change a lot, especially if we are not used to it. But when it's extremely hot, if proper measures aren't taken we could suffer a heat stroke or hyperthermia. Especially the youngest and the oldest, as well as the sick and the obese, are the population at highest risk.

Power consumption

During the hottest period our electricity consumption skyrockets, not in vain, we need to cool off and for this we plug in the fans and / or turn on the air conditioning. But this can be a problem, as the increased consumption can lead to power failures.

Most important heat waves

Heat wave in Europe, 2003

Heat wave in Europe, 2003

Chile, 2017

Between January 25 and 27, Chile experienced one of its worst heat waves in history. In the cities of Quillón and Cauquenes, the values ​​were very close to 45ºC, registering 44,9ºC and 44,5ºC respectively.

India, 2015

In the month of May, during the beginning of the dry season in India there were extreme temperatures of more than 47ºC, which led to the death of more than 2.100 people until the 31st of the month.

Europe, 2003

The 2003 heat wave was one of the most important for Europeans. Very high temperatures were recorded in southern Europe, with values ​​such as 47,8ºC in Denia (Alicante, Spain), or 39,8ºC in Paris (France).

Passed away 14.802 people between August 1 and 15.

Spain, 1994

During the last week of June and the first of July, in Spain, especially in the Mediterranean region, temperatures were very high, such as those in Murcia (47,2ºC), Alicante (41,4ºC), in Huelva (41,4ºC), or in Palma (Mallorca) 39,4ºC.

Tips to cope as well as possible

Drink lots of water to beat the heat

When there is a heat wave, you have to do whatever it takes to cope with it. Here are a few tips that may help you:

  • Stay hydrated: Do not wait until thirsty to drink water. With excess heat, fluids are lost rapidly, so it is essential that the body has a constant supply of water.
  • Eat fresh food: As much as you like hot dishes, during the summer and, above all, during the heat period, avoid eating them.
  • Put on sunscreenWhether you go to the beach or for a walk, human skin is very sensitive and can easily burn in the sun.
  • Avoid going out in the middle of the day: during this time the rays arrive much straighter, so they have a greater impact on the ground and, also, on the body.
  • Protect yourself from the sunWear light-colored clothing (light color reflects sunlight), wear sunglasses, and stay in the shade to avoid problems.

Heat waves are phenomena that can occur every year. It is essential to stay protected.

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