WMO Archive of Weather and Climate Extremes

In 2005, the television coverage of Hurricane Katrina, a deadly tropical cyclone that hit the North American coast near New Orleans, was both heartbreaking and enthralling to view.  As I watched, I was struck by a comment that I heard several times from different reporters:  “This is the worst hurricane of all time.”  Immediately, as an atmospheric scientist, I realized how false that statement was.  For example, while Katrina was deadly with over 1 800 killed, the dreadful 1970 tropical cyclone that struck what was then called East Pakistan (now Bangladesh) had a massive death toll of 300 000 people.  However, I aIso understood that an official death toll value or other information from an extreme weather event was something that was not easily uncovered or accessible to the general public.  At that time, there was no comprehensive, and official, database of weather and climate extremes addressing the “hottest,” “coldest,” “windiest,” “deadliest” and other extremes of our planet.

I contacted several of my colleagues (Jay Lawrimore, Roger Edwards and Chris Landsea) and we wrote an article on what was then considered the best-known and accepted weather and climate extremes for Earth for the Bulletin of the American Meteorological Society (Cerveny et al. 2006).  In that article, we also advocated for the creation of an official global database of weather and climate extremes.   Shortly after its publication, I received a call from Thomas Peterson, who later became President of the WMO Commission for Climatology (CCl).  He asked me to present the CCl subgroup of which he was then chair with a proposal for an official WMO Archive of Weather and Climate Extremes .  I did so and, in 2007, CCl established the WMO World Weather and Climate Extremes Archives (wmo.asu.edu/).

One important question should be addressed before going into detail on the Archive: “Why do we actually need a world archive of weather extremes?” There are six major reasons:

  • Probably most importantly, knowledge of our existing weather and climate extremes is critical in determining exactly how much and how fast our world’s climates are changing.  Knowledge of extremes establishes our baselines so that we can access exactly how our climate is changing.  For example, in 2015, a massive heat wave along the peninsula coast of Antarctic lead to the highest temperature (17.5 °C) ever recorded for the continental area of Antarctica and its nearby island (Skansi et al. 2017).  Our Archive is being updated much more frequently than any of us in the early days of this Archive project thought possible.
  • Knowledge of weather and climate extremes is critically important for medical and engineering concerns.  For example, if a person is designing a building or bridge, knowing exactly how fast the wind speeds can actually reach is essential.  Similar concerns exist with temperature and other weather variables.  How hot can our temperatures reach?  How cold?  Our bodies operate within a specified set of conditions and the Archive helps to define those conditions.
  • Our evaluation of world weather and climate extremes can sometimes advance our basic atmospheric sciences.  For example, one of our recent investigations on the longest distance and duration lightning strikes has caused a long-standing fundamental meteorological definition of “lightning” to be rewritten (Lang et al. 2016).
  • As mentioned above, there is a tendency for the media sometimes to “overhype” an event – particularly a weather event.  We need official and accessible records of weather extremes to aid the media in putting weather events in proper perspective!
  • Perhaps surprisingly to some, many locales actually commemorate and recognize the occurrence of major weather events.  For example, a huge sign at Mount Washington Observatory in New Hampshire, USA, acknowledged their long-held record for the highest wind recorded (231 m/h or 372 km/h), only recently exceeded by a wind gust at a small island off Australia (see Courtney et al. 2012).  Other locales have similar recognition of their extremes.
  • Lastly, people in general are fascinated by weather and, in particular, they love weather extremes – the hottest, the coldest, the windiest and so on.  So having a reliable list of these extremes helps foster people’s interest in weather. In particular since the inception of the WMO Archive or Weather and Climate Extremes, I have found that children love to hear about weather extremes.  Grabbing kids’ interest in weather through these extremes promotes possible future careers in the atmospheric sciences and ensures that we will have quality meteorologists and climatologists for the future.

However, while some individual countries have their own committees for determining national weather records, until 2007 there was nothing official for the world. The WMO Archive maintains official records of the world, hemispheric and regional extremes associated with a number of specific types of weather.  Presently, the Archive lists extremes for temperature, pressure, rainfall, hail, wind, and lightning as well as two specific types of storms, tornadoes and tropical cyclones. One common weather variable, snowfall, is not listed because of potential issues in consistent official measurement around the world.


Evaluation process

At the time of the Archive’s creation, we expected that we might have to evaluate a new record every few years.  Since 2007, we have actually evaluated more than fifteen potential records in a process that has become codified over the past decade.

Following an initial assessment of a new potential extreme and available evidence by the leadership of the CCl and the Rapporteur of Weather and Climate Extremes, an ad-hoc evaluation committee of international top atmospheric scientists is assembled.  In the years since its inception, we have had committees comprised of scientists from countries including Argentina, Armenia, Australia, Bangladesh, Canada, China, Colombia, Cuba, Egypt, France, Germany, India, Israel, Italy, Japan, Kuwait, Libya, Mauritius, Mexico, Mongolia, Morocco, New Zealand, Pakistan, South Africa, Spain, Sweden, Switzerland, Turkey, United Kingdom, United States, Zimbabwe and several other Members of the WMO.

A photocopy of the original observer's log sheet for Azizia A photocopy of the original observer's log sheet for Azizia in September 1922 showing the misplaced temperature values for the purported record temperature recorded on 22 September 1922.

The members of these committees are selected for a range of specific expertise, including local climate knowledge, understanding of factors contributing to an extreme occurring at a particular location or specific climate phenomena for the world in general, and specialized knowledge.  The Rapporteur, in conjunction with a committee member from the local area of the potential extreme and others, constructs a background report of the available information and data regarding the extreme observation.  This report includes specifics on the exact geographic position of the observation, the type of equipment used to make the observation (and specifics on its calibration, maintenance and operation), the synoptics (regional weather) of the event and any notable unusual or unique information concerning the observation.  The committee reviews the report and discusses all aspects of the potential extreme, addressing five key questions:

  1. Is there need for more raw data or documentation on this event to determine its validity or invalidity?  Are there other data or other analyses corresponding to this time/place extreme event?
  2. Are there any concerns as to equipment, calibration, measurement procedures, or other processes/procedures associated with the measurement of the event?
  3. Are there any concerns associated with the nature of the event (massive continental high pressure) that would raise questions regarding the validity of the record?
  4. Are there any other concerns associated with the event?
  5. Fundamentally, does the documentation support or refute this current world weather record?

Thus far, such discussions have been via email with the Rapporteur as moderator.  After their deliberations, the committee recommends a finding to the Rapporteur for final judgment and the observation is either accepted for inclusion into the Archive or dismissed.

Famous records

A two-year investigation into the long-standing temperature observation of 58 °C recorded in 1922 at El Azizia, in then Italian-controlled Libya (El Fadli et al. 2013), was one of the most famous.  An international committee of 13 scientists, including scientists from Italy and Libya, concluded that the observation was invalid because of an error in recording the temperature. The announcement followed a danger-fraught investigation during the 2011 Libyan revolution.  The committee had five major concerns with the record:

  • problematical instrumentation
  • a likely inexperienced observer
  • an observation site over an asphalt-like material that was not representative of the native desert soil
  • poor matching of the extreme to other nearby locations
  • poor matching to subsequent temperatures recorded at the site.
Longest duration and distance lightning flashes
Maps indicating the geographic locations of the verified longest duration and longest distance lightning flashes for the Earth

The committee concluded that the most compelling scenario for the 1922 event was that a new and inexperienced observer, not trained in the use of an unsuitable replacement instrument that could be easily misread, improperly recorded the observation and was consequently in error by about 7 °C. The announcement made world news.  Following the press announcement on 13 September 2012, the WMO Extremes website traffic jumped from averaging 150 hits per day to over 24 000 hits over a three-day period.  A secondary peak occurred four months later when the New York Times wrote a follow-up story on the announcement (Shimizu et al. 2014).

Several other investigations have garnered equal interest:

A new record was accepted in 2011 for highest non-tornadic wind gust – A measurement of 408 km/h was made by an automatic recording station during Tropical Cyclone Olivia on 10 April 1996 at Barrow Island, Australia. The long-standing record had been 372 km/h, registered in April 1934 across the summit of Mount Washington, USA.  The evaluation panel included members from Australia and from Mount Washington Observatory (Courtney et al. 2012).

Two world rainfall records established in 2009 for La Réunion associated with the passage of the intense Tropical Cyclone Gamede in 2007 – First, an extreme rainfall rate of 3 929 mm over 72 hours recorded at Cratère Commerson became the world-record rainfall for that period. Second, a Cratère Commerson rain gauge registered a world-record rainfall total of 4 869 mm over a 4-day (96 hour) period (Quetelard et al. 2009).

A Western Hemispheric record was established in 2012 for a hailstone of 0.879 kg or 1.9375 pounds (diameter: 203.2 mm 8.0 inches) that fell on 23 July 2010 in Vivian, South Dakota, USA. However, the world’s heaviest hailstone still remains the 1.02kg (2.25lb) hailstone that fell on 14 April 1986 in Gopalganj district, Bangladesh.

A wave height record was accepted in 2014, specifically “Highest Significant Wave Height as measured by a Buoy” –  A significant height of 19 metres (62.3 feet) was recorded by an automated buoy at 0600 UTC on 4 February 2013 in the North Atlantic Ocean.  The recording buoy is a part of the Met Office (UK) Marine Automatic Weather Stations (MAWS) network.  This extreme wave height value was recorded following the passage of a very strong cold front that produced winds up to 43.8 knots (22.5 m/s or 50.4 mph).

Two records were accepted in 2016 for (a) the longest reported distance and (b) the longest reported duration for a single lightning flash in, respectively, Oklahoma (United States of America) and southern France – The lightning flash over Oklahoma in 2007 covered a horizontal distance of 321 km (199.5 miles). The lightning event over southern France in 2012 lasted continuously for 7.74 seconds (Lang et al. 2016).

Three new records for the highest temperatures recorded in the Antarctic Region were accepted by the WMO in 2017 – The highest temperature for the “Antarctica Region” (defined by the WMO and United Nations as all land and ice south of 60°S) of 19.8 °C (67.6 °Fahrenheit) was observed on 30 January 1982 at Signy Research Station, Borge Bay on Signy Island.  The highest temperature for the “Antarctic continent” (defined as the main continental landmass and adjoining islands) is the temperature extreme of 17.5 °C (63.5 °F) recorded on 24 March 2015 at the Argentine Research Base Esperanza located near the northern tip of the Antarctic Peninsula.  Thirdly, the highest temperature for the Antarctic Plateau [at or above 2500 meters (8202 feet)] was the observation of -7.0 °C (19.4 °F) made on 28 December 1980 at an Automatic Weather Station (AWS) site D-80 located inland of the Adélie Coast.  The lowest temperature yet recorded by ground measurements for the Antarctic Region, and for the whole world, remained the record of −89.2 °C at Vostok station on 21 July 1983 (Skansi et al. 2017).

In 2017, an evaluation committee completed an in depth investigation of existing mortality records for five specific weather-related events in order to determine the highest documented death tolls associated with each event – The five identified and verified historical mortality extremes are the following:

  • “Highest mortality (indirect strike) associated with lightning” - 469 people killed in a lightning-caused oil tank fire in Dronka, Egypt, on 2 November 1994
  • “Highest mortality directly associated with a single lightning flash” - 21 people killed by a single stroke of lightning in a hut in Manica Tribal Trust Lands in Zimbabwe (at the time of incident, Rhodesia) on 23 December 1975
  • “Highest mortality associated with a tropical cyclone” - an estimated 300 000 people killed directly as result of the passage of a tropical cyclone through Bangladesh (at time of incident, East Pakistan) of 12/13 November 1970
  • “Highest mortality associated with a tornado”- an estimated 1 300 people killed by the 26 April 1989 tornado that destroyed the Manikganj district, Bangladesh
  • “Highest mortality associated with a hailstorm” - 246 people killed as a result of a severe hailstorm occurring near Moradabad, India, on 30 April, 1888 (Cerveny et al. 2017).

Currently, a couple of investigations are ongoing regarding very high temperatures in 2016 in Kuwait and Pakistan and extremely strong winds recorded over Japan in 2004.


A living repository

A key consideration is that all extremes in the WMO Archive are accepted and listed until or unless critical evidence is presented to either refute an existing record or substantiate a new record.  In other words, the Archive is a living repository.  In a world undergoing climate change, new records are being made every day and it is the duty and responsibility of the Archive to ensure that the world’s records of weather and climate extremes are as complete, accurate, and up-to-date as possible.  Indeed, since its inception, the WMO Archive is now routinely queried by other “record-keeping” entities, such as the Guinness Book of World Records, for our expertise involving weather records.

Study and adjudication of world weather and climate records has proven to be very useful activity for both the scientific community and general public.  It has increased public awareness of the activities of WMO, and provided a valuable service to a variety of people and organizations outside of the atmospheric science community.  

Within the global atmospheric science organization, the work of the WMO Archive has truly helped to advance the science.  Through analysis of new extremes made possible by new technologies, such as our lightning distance and duration extremes, and through analysis of traditional data sources and instrumentation (such as the investigation of temperature  and wind extremes), the investigations of the many scientists contributing to Archive allows us to reanalyse new, as well as past, weather records in much more detail and with greater precision than ever before.  Fundamentally, the final result is an even better set of data for analysis of important global and regional questions involving climate change.  With the continued support and incredible work of the many scientists comprising the multitude of ad hoc evaluation committees, the WMO will continue to set the standard for global monitoring and adjudication of weather and climate extremes.



Cerveny, R.S. and Pierre Bessemoulin, Christopher C.  Burt, Mary Ann Cooper, M.D., Zhang Cunjie, Ashraf Dewan, Jonathan Finch, Ronald L. Holle, Laurence Kalkstein, Andries Kruger, Tsz-cheung Lee, Rodney Martínez, M. Mohapatra, D.R. Pattanaik, Thomas C. Peterson, Scott Sheridan, Blair Trewin, Andrew Tait, M.M.Abdel Wahab, 2017: WMO Assessment of Weather and Climate Mortality Extremes:  Lightning, Tropical Cyclones, Tornadoes, and Hail, J. Wea. Clim. Soc. doi.org/10.1175/WCAS-D-16-0120.1

Cerveny, R.S., J. Lawrimore, R. Edwards, C. Landsea 2006: Extreme Weather Records:  Compilation, Adjudication and Publication, Bulletin of the American Meteorological Society 88 (6): 853-860.

Courtney, J., Steve Buchan, Randall S. Cerveny, Pierre Bessemoulin, Thomas C. Peterson, Jose M. Rubiera Torres, John Beven, John King, Blair Trewin, and Kenneth Rancourt, 2012: Documentation and Verification of the World Extreme Wind Gust Record:  113.3 m s-1 on Barrow Island Australia during passage of Tropical Cyclone Olivia, Australian Meteorological and Oceanographic Journal, 62(1): 1-9.

El Fadli, K, R.S. Cerveny, C.C. Burt, P. Eden, D. Parker, M. Brunet, T.C. Peterson, G. Mordacchini, V. Pelino, P. Bessemoulin, J.L. Stella, F. Driouech, M.M Abdel wahab, M.B. Pace, 2013: World Meteorological Organization Assessment of the Purported World Record 58ºC Temperature Extreme at El Azizia, Libya (13 September 1922), Bulletin of the American Meteorological Society. doi: dx.doi.org/10.1175/BAMS-D-12-00093.1 (print version in Feb, 2013)

Lang, T.J., Stéphane Pédeboy, William Rison, Randall S. Cerveny, Joan Montanyà, Serge Chauzy, Donald R. MacGorman, Ronald L. Holle, Eldo E. Ávila, Yijun Zhang, Gregory Carbin, Edward R. Mansell, Yuriy Kuleshov, Thomas C. Peterson, Manola Brunet, Fatima Driouech, and Daniel S. Krahenbuhl, 2016: WMO World Record Lightning Extremes: Longest Reported Flash Distance and Longest Reported Flash Duration,  Bulletin of the American Meteorological Society, dx.doi.org/10.1175/BAMS-D-16-0061.1

Quetelard, H., Bessemoulin, P., Cerveny R.S., Peterson, T.C., Burton, A., and Y. Boodhoo, 2009, World record rainfalls (72-hour and four-day accumulations) at Cratère Commerson, Réunion Island, during the passage of Tropical Cyclone Gamede, Bulletin of the American Meteorological Society, 90(5): 603-608

Shimizu, M., Randall S. Cerveny, Elizabeth A. Wentz, Kevin E. McHugh, 2014: Geographic and Virtual Dissemination of an International Climatic Announcement, Bulletin of the American Meteorological Society, 95(7):987-989.

Skansi, M. de Los Milagros, John King, Matthew A. Lazzara, Randall S. Cerveny, Jose Luis Stella, Susan Solomon, Phil Jones, David Bromwich, James Renwick, Christopher C. Burt, Thomas C. Peterson, Manola Brunet, Fatima Driouech, Russell Vose, and Daniel Krahenbuhl, 2017: Evaluating Highest Temperature Extremes for the Antarctic Region.  EOS Earth & Space Science News (American Geophysical Union), 97: doi.org/10.1029/2017EO068325.


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