French Station Breaks All-Time Heat Record by Astounding Margin

June 30, 2019, 8:16 PM EDT

Above: Catherine Bernard, wine producer, looks at her heat-damaged vines on Sunday, June 30, 2019, in Restinclieres, near Montpellier, in the South of France. Montpellier broke their all-time heat record by an astonishing 5.8°C (10.4°F) on June 28. Winegrowers in the south of France said their precious crops had been badly damaged after six days of intense heat that fuelled huge blazes and pollution peaks and officially claimed four lives in France. Image credit: Sylvain Thomas/AFP/Getty Images.

Not only was Friday, June 28, 2019 the hottest day in French history, it also featured record-breaking heat so extreme that only one other heat wave in world history can match it. The temperature at Montpellier-Fréjorgues airport hit 43.5°C (110.3° F) on June 28, 2019, breaking the station’s previous record by a truly incredible 5.8° C (10.4° F). The station’s period of record extends back 74 years, to 1946.

Usually, when a station with a long period of record beats its all-time mark, the new record is at most a degree or two Fahrehneit beyond the old record. In rare cases, the new record will exceed the old one by five or more degrees. It is nearly unheard of for the record to be broken by more than 10°F. Indeed, weather records expert Maximiliano Herrera said in an email that there is only one other case in world history of a station with a long period of record having a heat wave with a larger spread between the first- and second-place marks: on July 6, 1936, the temperature in Steele, North Dakota, soared to 121°F (49.4°C), the highest temperature ever recorded in the state of North Dakota. Steele’s second highest temperature (except in the same heat wave in 1936) was only 110°F (43.3°C) in 1934. So, the temperatures in the 1936 heat wave beat the station’s second-place heat wave by an incredible margin of 11°F (6.1°C).

Since temperatures in the U.S. are measured to the nearest degree F, we can say that last Friday’s margin of record at Montepellier virtually tied a world record, considering that the Steele, ND, measurement had a higher margin of imprecision.

Breaking a heat record by 5°C (8°F): a rare occurrence

The 5°C (8°F) margin between the all-time heat record and the second-place heat mark was beaten at one other station in France on Friday: a 45.1°C (113.2°F) mark at Marsillargues, which beat the previous record of 39.7°C (103.5°F) set on Jun 21, 2003 by 5.4°C (9.7°F). The station’s period of record was not as long, at 32 years.

According to Herrera, there are only a few other cases globally of heat records being broken by over 5°C (8°F). All of these occurred in the U.S. in 1936. In addition, in July 1983, Testy, Kazakhstan recorded a maximum temperature 5°C (8°F) higher than its second highest temperature, a difference that still stands today. Temperature margins between the all-time high and second-highest temperature just below the 8°F (5°C) threshold were also set in the central U.S. in 1930, 1934, and 1954, and in Canada in 1937.

The widespread heat that attacked the U.S. Great Plains in the 1930s, including a number of all-time state highs that remain in place today, occurred in tandem with the Dust Bowl. The denuding of the Plains landscape—which occurred largely due to poor land management—was a major factor in allowing surface heat to reach the levels it did. As for the recent heat wave in Europe, where no such dust bowl occurred, it is just the latest in a series of record-smashing heat episodes affecting various parts of Europe over the last 16 years.

There is strong evidence that human-produced greenhouse gases have already raised the odds of record-setting heat waves. Such episodes will hit some locations harder and sooner than others, due to the vagaries of multi-year and multi-decadal weather patterns, but societies around the world need to prepare for the consequences of increasing record heat—and work to reduce the fossil-fuel emissions that are making such heat ever more likely.

High temperatures across southern France on 6/28/2019
Figure 1. High temperatures in southern France on Friday, June 28, 2019. Circled in yellow are those stations that beat or tied the previous all-time national record of 44.1°C. Image credit: Courtesy Etienne Kapikian, Météo-France).

More details on the French heat wave of June 28, 2019

France set its all-time heat record on Friday, when the mercury shot up to an astonishing 45.9°C (114.6°F) at Gallargues-le-Montueux in southern France. This destroyed the previous all-time national heat record of 44.1°C (111.4°F), set on Aug. 12, 2003, by 1.8°C (3.2°F), according to Météo-France. At least two other stations in southern France on Friday beat the former national record by at least 1°C as well: Villevielle, with 45.4°C, and Marsillargues, with 45.1°C. According to an email from Etienne Kapikian (Météo-France), a remarkable 14 stations in the primary French observing network of nearly 600 stations beat or tied the former all-time national French heat record of 44.1°C. All of these stations had a period of record of at least 30 years. These stations include:

45.9°C: Gallargues-le-Montueux (Gard)
45.4°C: Villevieille (Gard)
45.1°C: Marsillargues (Hérault)
44.6°C: Saint-Chamas (Bouches-du-Rhône)
44.5°C: Varages (Var)
44.4°C: Nîmes-Courbessac (Gard), Prades-le-Lez (Hérault), Peyrolles-en-Provence (Bouches-du-Rhône)
44.3°C: Carpentras (Vaucluse), Istres (Bouches-du-Rhône), Moulès-et-Baucels (Hérault), Vinon-sur-Verdon (Var), Cadenet (Vaucluse)
44.1°C (tie): Nîmes-Garons airport (Gard)

In all, 22 major French stations set new all-time heat records on Friday; another six did so on Thursday, and one on Wednesday.

All-time national heat record also set in Andorra

Friday’s extreme heat also affected northeastern Spain and the tiny Principality of Andorra, sandwiched between France and Spain. Andorra set their all-time national heat record on Friday with 39.4°C (102.9°F) at Borda Vidal. According to weather records expert Maximiliano Herrera, the previous national heat record was 38.5°C (101.3°F) at the capital city of Andorra La Vella on July 16, 2005.

A significant record

All-time national heat and cold records are difficult to beat, particularly in a country with a dense observational network with many stations that have a long period of record, like France. Three remarkable features stand out about the new record:

  • It was destroyed by a huge margin: 1.8°C (3.2°F).
  • The record was beaten in the month of June, several weeks before Europe’s climatological peak heat of late July. In the list of all-time European heat records maintained by Maximiliano Herrera,  just three of the 53 all-time national European heat records have been set in June. Twenty-two were set in July, and 27 were set in August.
  • The former national record was beaten or tied by at least 14 French stations on Friday.

How trustworthy is France's new heat record?

As the French heat wave made global headlines this past weekend, there was a scattering of social-media posts minimizing the importance of the extreme records detailed above. One area of debate was the contrast between the high of 44.1°C (111.4°F) recorded at a rooftop station in Gallargues-le-Montueux and the new national record of 45.9°C (114.6°F) recorded at a nearby surface station. In a Facebook post on Sunday, the French association Infoclimat called out several important points:

  • The rooftop station is a citizen-maintained site, part of the Infoclimat network, and its temperature sensor is not regularly recalibrated in line with national and global weather observing standards.
  • The northerly surface flow that brought record-hot temperatures included a strong downslope (foehn) component, which can lead to sharp temperature variations over small distances, both horizontally and vertically.

An article by French meteorologist and author Guillaume Séchet on the website meteo-paris.com included details and photos of the surface station, which is a second-order Meteo­-France station (meaning that its data are not available online in real-time without a fee). The thermometer is sheltered and located at least 1.5 meters above ground, in line with Météo-France standards. Photos show vegetated ground extending in all directions from the site. In terms of its siting quality, the station is rated 3 by Météo-France on a scale of 1 to 5, where 1 is a “gold standard” reference site and 5 is unsuitable for professional use. The rating of 3 implies a potential temperature error of at most +/- 1°C, which is less than the spread between Friday’s observation and the previous all-time national record. Moreover, according to meteo-paris.com, the rating of 3 appears to have been triggered at least in part by the presence of a canal about 16 meters (52 feet) south of the observing site. As it turns out, the north winds present on Friday would have minimized any potential influence from the canal, which if anything would have reduced rather than enhanced the record-high reading.

Based on this analysis, there is no obvious reason to doubt that France’s highest reliable temperature on record was broken on Friday at Gallargues-le-Montueux. Just as important is the stunning extent of multiple sites that all broke France’s previous national record. As Kapikian points out, “No less than 3 Meteo-France stations (+ non-professional Le Triadou's 46.1°C) recorded a high above 45°C in that precise area of Languedoc. Vineyards got partially grilled by the hot dry air in that area. Weather models had clearly pointed towards this specific area (border between Gard and Hérault, slightly inland) as having the most obvious chance of reaching 45°C or a bit more….This is not a random temperature out of nowhere.”

Yet more heat records were smashed across Germany and nearby countries on Sunday, as we’ll discuss in a post on Monday.

Bob Henson co-wrote this post.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Dr. Jeff Masters

Dr. Jeff Masters co-founded Weather Underground in 1995 and flew with the NOAA Hurricane Hunters from 1986 to 1990. He authors the blog "Eye of the Storm" at Scientific American.

weatherman.masters@gmail.com

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