A heat wave or heatwave, sometimes described as extreme heat, is a period of abnormally hot weather. A time period of five consecutive days is often used to define a heat wave but the exact definition of a heat waves can vary for different countries. A heat wave is usually measured relative to the usual climate in the area and to normal temperatures for the season. Temperatures that humans from a hotter climate consider normal, can be regarded as a heat wave in a cooler area. This would be the case if the warm temperatures are outside the normal climate pattern for that area. High humidity often occurs during heat waves as well. This is especially the case in oceanic climate countries. Heat waves have become more frequent, and more intense over land, across almost every area on Earth since the 1950s, the increase in frequency and duration being caused by climate change.
The 2003 European heat wave saw the hottest summer recorded in Europe since at least 1540. France was hit especially hard. The heat wave led to health crises in several countries and combined with drought to create a crop shortfall in parts of Southern Europe. The death toll has been estimated at more than 70,000.
The 2006 European cold wave was an unusual and deadly cold wave which resulted in abnormal winter conditions over much of Europe. Southern Europe saw cold and snow, while places in northern Norway saw abnormally mild conditions. The phenomenon started in early January 2006, in the region of the Polar Urals, with temperatures nosediving below -50°C, and extended to west Russia, then Central Europe where parts of Poland, Slovakia, and Austria saw temperatures drop below -30 °C. The cold wave resulted in the deaths of up to 50 people in Russia, and a significant death toll in Eastern Europe, including Ukraine, Moldova, and Romania. The abnormal conditions gradually abated towards the end of the month. According to Munich Re reinsurance company, it was the deadliest cold snap between 1980 and 2011, causing 790 fatalities throughout Europe. According to the International Federation of Red Cross and Red Crescent Societies, there were 884 deaths in Ukraine, 135 in Moscow, 13 in Moldova and 5 in Belarus, and over 20,000 cases of frostbite were treated in the region's hospitals. The damage to Russian crops due to severe frost was estimated at $929 million.
The 2007 European heat wave affected most of Southern Europe and the Balkans. The phenomenon began affecting Italy and Turkey on 17 June and expanded into Greece and the rest of the Balkans, Hungary and Ukraine on 18 June. The costs of the heat wave were estimated at 2 billion euros.
The 2010 Northern Hemisphere summer heat waves included severe heat waves that impacted most of the United States, Kazakhstan, Mongolia, China, Hong Kong, North Africa and the European continent as a whole, along with parts of Canada, Russia, Indochina, South Korea and Japan during July 29, 2010. The first phase of the global heatwaves was caused by a moderate El Niño event, which lasted from June 2009 to May 2010. This lasted only from April 2010 to June 2010 and caused only moderate above-average temperatures in the affected regions, but it also set new record high temperatures for most of the area affected in the Northern Hemisphere.
The 2013 heatwave in the United Kingdom and Ireland was a period of unusually hot weather primarily in July 2013, with isolated warm days in June and August. A prolonged high pressure system over Great Britain and Ireland caused higher than average temperatures for 19 consecutive days in July, reaching 33.5 °C (92.3 °F) at Heathrow and Northolt.
The 2018 Britain and Ireland heatwave was a period of unusually hot weather that took place in June, July and August. It caused widespread drought, hosepipe bans, crop failures, and a number of wildfires. These wildfires worst affected northern moorland areas around the Greater Manchester region, the largest was at Saddleworth Moor and another was at Winter Hill, together these burned over 14 square miles (36 km2) of land over a period of nearly a month.
The 2018 European drought and heat wave was a period of unusually hot weather that led to record-breaking temperatures and wildfires in many parts of Europe during the spring and summer of 2018. It is part of a larger heat wave affecting the northern hemisphere, caused in part by the jet stream being weaker than usual, allowing hot high-pressure air to linger in the same place. According to the European Drought Observatory, most of the areas affected by drought are across northern and central Europe. According to the World Meteorological Organization, the severe heat waves across the northern hemisphere in the summer of 2018, are linked to climate change in Europe, as well as events of extreme precipitation.
In 2018, several heat waves with temperatures far above the long-time average and droughts were recorded in the Northern Hemisphere: The earth's average surface temperature in 2018 was the fourth highest in the 140 years of record keeping. It is assumed that the jet stream is slowing down, trapping cloudless, windless and extremely hot regions of high pressure. The jet stream anomalies could be caused by polar amplification, one of the observed effects of global warming.
A tropical night is a term used in many European countries to describe days when the temperature does not fall below 20 °C (68.0 °F) during the nighttime. This definition is in use in countries including the Austria, Croatia, Denmark, Finland, Germany, Greece, Hungary, Italy, the Republic of Ireland, Latvia, Lithuania, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Spain, Sweden and the United Kingdom. In the United States, by contrast, the term sultry nights is used when the temperature does not fall below 27 °C (80.6 °F) in the Gulf and Atlantic states.
In late June and late July 2019 there were two temporally distinct European heat waves, which set all-time high temperature records in Belgium, France, Germany, Luxembourg, the Netherlands, and the United Kingdom.
The 2021 Britain and Ireland heat wave was a period of unusually hot weather in July 2021 that led to record-breaking temperatures in the UK and Ireland.
In 2022, several areas of the world experienced heat waves. Heat waves were especially notable in East Asia, the Indian subcontinent, Australia, western Europe, the United States, and southern South America. 2022 heat waves accounted for record-breaking temperatures and, in some regions, heat-related deaths. Heat waves were worsened by the effects of climate change, and they exacerbated droughts and wildfires.
The 2022 United Kingdom heatwaves were part of several heatwaves across Europe and North Africa. The United Kingdom experienced three heatwaves; the first was for three days in June, the second for three days in July, and the third for six days in August. These were periods of unusually hot weather caused by rising high pressure up from the European continent. There were also more grass fires and wildfires than average, and in August a drought was declared in many regions.
From June to August 2022, persistent heatwaves affected parts of Europe, causing evacuations and killing tens of thousands. These heat waves were the deadliest meteorological events in 2022. The highest temperature recorded was 47.0 °C (116.6 °F) in Pinhão, Portugal, on 14 July.
In mid-January 2022, the Southern Cone had a severe heat wave, which made the region for a while the hottest place on earth, with temperatures exceeding those of the Middle East. This extreme weather event was associated with the Atlantic anticyclone, a particularly intense La Niña phenomenon in the Pacific Ocean, and the regional effects of climate change.
A number of heat waves began across parts of the northern hemisphere in April 2023, many of which are ongoing. Various heat records have been broken, with July being the hottest month ever recorded.
In 2023, Europe had been affected by heat waves. The most significant of which was the named heat wave, Cerberus Heatwave, which brought the hottest temperatures ever recorded in Europe. Starting on 10 July 2023, the record-breaking Cerberus anticyclone affected many European countries, with the effects felt most severely in parts of Southeast and Southwest Europe such as Cyprus, Greece, Italy, and Spain. The private Italian weather website iLMeteo named the extreme weather event after the hound of Hades from Greek mythology, and although some reports link the naming to the Italian Meteorological Society, the society's president said that they "absolutely don't use it".
Throughout late March and April 2024, Europe was affected by abnormally high temperatures that reached the summer average. National records for spring temperatures were broken in mainly Eastern European and Southeastern European countries. During March, eight countries had broken temperature records with Moldova reporting the highest 29.7 °C in Sîngerei followed by Albania at 29.6 °C in Kuçovë, Croatia at 29 °C in Osijek, and Belarus at 27.2 °C in Lyelchytsy. The heatwave continued into April with temperatures going above 30 °C in southern parts of Europe making it the first-ever daytime record in April. The highest was recorded in Zenica, Bosnia & Herzegovina, at 33.3 °C on April 14, 2024. After two weeks of persistent heat, a cold spell occurred. It lasted for 10 days and brought late frost in some areas. With Zagreb, Croatia measuring -0,4 °C at April 22 just after measuring 30,5 °C on April 14, which tied April record form 2012. The cause of the heatwave was a stream of hot air from Africa.
