Climate of Buenos Aires

View of Buenos Aires from the air.
View of Buenos Aires from the air

Buenos Aires has a temperate climate, which is classified as a humid subtropical climate (Cfa) under the Köppen climate classification with 4 distinct seasons. Summers are hot and humid with frequent thunderstorms while winters are cool and drier with frosts that occurs on average twice per year. Spring and fall are transition seasons characterized by changeable weather. At the central observatory, the highest recorded temperature is 43.3 °C (109.9 °F)[1] while the lowest recorded temperature is −5.4 °C (22.3 °F) on July 9, 1918.[2]

Different climatic factors influence the climate of Buenos Aires. The semi–permanent South Atlantic High influences its climate throughout the year by bringing in moist winds from the northeast, which brings most of the precipitation to the city in the form of frontal systems during winter or storms produced by Cyclogenesis in autumn and winter. The hot temperatures and high insolation in the summer months forms a low pressure system over northern Argentina, generating a pressure gradient that brings moist easterly winds to the city and because of this, summer is the rainiest season. In contrast, this low pressure system weakens in the winter, which combined with strong southerly winds results in a drier season due to weaker easterly winds. Being located in the Pampas, Buenos Aires has variable weather due to the passage of contrasting air mass; the cold, dry Pampero from the south and warm, humid tropical air from the north. The coastal location results in a strong maritime influence, causing hot and cold days to be rare.

General climatology

Buenos Aires is located in the humid subtropical climate zone (Köppen climate classification: Cfa).[3][4] Due to the maritime influences,[5] its climate is temperate with hot and cold days being rare.[6] The climate of Buenos Aires is dominated by the semi–permanent South Atlantic High throughout the year.[3] This brings in moist winds from the northeast, which brings most of the precipitation to the city.[3] During winter, it brings in frontal systems responsible for precipitation in the city.[3] In autumn and summer, it produces storms that are generally located north of the city although it produces strong winds from the south or southeast that can occasionally lead to the swelling of the Río de la Plata, which can flood coastal areas.[3]

As well, it is located in an area in which the Pampero and the Sudestada winds pass by.[7] Being located in the Pampas, the weather is variable due to the contrasting air masses and frontal storms.[8] The Pampero wind brings in cold, dry air from the south while warm humid tropical air produces sultry nortes.[8][9] Often, the passage of the Pampero winds occurs as a cold front passes through, leading to strong gusts from the south or southeast, a decrease in humidity and temperature, and an increase in the atmospheric pressure.[9] When the cold pampero winds meet with warm humid air from the north, thunderstorms are produced.[8] The Sudestada winds are formed when a high pressure system located in southern Argentina interacts with a low pressure system over Uruguay and southern Brazil.[10] When sudestadas form, they bring long periods of precipitation, cloudy weather and cooler temperatures.[11][12][13] These are common during the winter months.[13]

The urban heat island influences the climate of the city with the city being warmer than suburban and rural areas.[14] On average, Buenos Aires is warmer than the surrounding areas by 1.5 to 3.5 °C (2.7 to 6.3 °F).[14] The average heat island is smaller than in winter.[15] This varies by time with the urban heat island effect during the day being the strongest in July than in January.[15] In contrast, the urban heat island effect during nights is the most intense in January than July.[15]

The El Niño–Southern Oscillation is a major factor in the variation of in annual precipitation within Buenos Aires and the Pampas, particularly during spring and summer.[16][17] During an El Niño year, precipitation is higher,[17] with a significant increase in precipitation from November–January.[18] In contrast, La Niña years are associated with lower precipitation,[17] in which precipitation is below average during October–December.[18]

Seasonal Weather

Spring

Jacarandas in bloom at Plaza Miserere, Buenos Aires during Spring
Jacarandas in bloom at Plaza Miserere, Buenos Aires

Springs in Buenos Aires are usually mild during the day with cool to cold nights.[19] The average high is 22.2 °C (72.0 °F) while the average low is 12.7 °C (54.9 °F).[19] It is one of the rainiest season in the city, averaging 300.9 mm (11.85 in) of precipitation and 26 days with measurable precipitation.[19] Nonetheless, most precipitation events are short in duration.[6]

Spring is characterized by changeable weather with temperatures that can fluctuate.[20] Cold polar air from the south can bring cooler temperatures. An extreme example of this was in November 2007, when cold polar air from the south brought temperatures down to 2.5 °C (36.5 °F) on the morning of November 15.[21] The same polar air affected many parts of the country, bringing cold temperatures and snow in coastal parts of Patagonia.[21] In contrast, hot humid air from the north produces sultry days;[8] the highest temperature recorded in spring is 36.8 °C (98.2 °F).[19] In some cases, heat waves, which is defined when there are 3 consecutive days in which the minimum and maximum temperature exceed 22.0 °C (71.6 °F) and 32.3 °C (90.1 °F) respectively can occur, particularly in November.[22]

Summer

Map showing the location of the South American Tornado Alley. Most this occurs in the eastern parts of the country. Areas in gray have a high risk of tornadoes; areas in red have a moderate risk.
Location of the South American "Tornado Alley" (Spanish: Pasillo de los Tornados). Areas in gray have a high risk of tornadoes; areas in red have a moderate risk. Buenos Aires is located in the moderate risk zone for tornados

Summers are hot and humid.[6] On average, mornings and afternoons are hot while temperatures drop considerably during nighttime.[6] January is the warmest month.[23] The average high is 28.9 °C (84.0 °F) while the average low is 18.9 °C (66.0 °F).[1] With a mean precipitation of 341.6 mm (13.45 in), it is the rainiest season.[1] This is due to hot temperatures and high insolation that lead to the development of a low pressure system called the Chaco Low situated over northern Argentina that interacts with the South Atlantic High to generate a pressure gradient that brings moist easterly winds to the region, favouring precipitation, which mostly occurs in the form of convective thunderstorms.[24][25] It is also the season with the most clear days, the least foggiest and the one with the most stormy days.[23]

Heat waves are a common feature of summers in the city.[1] These heat waves place extra demand on electricity usage, leading to shortages.[26][27] In extreme cases, these power shortages during heat waves can cause traffic jams and protests, such as the December 2013 heat wave, which was the longest heat wave ever recorded in Buenos Aires since the start of observations in 1906.[27][28] However, most heat waves are of short duration (usually less than a week),[1] and are followed by the passage of the cold, dry Pampero wind, which brings rain and thunderstorms due to the 2 contrasting air masses meeting followed by cooler temperatures and lower humidity.[8][9][29] Often, the passage of the Pampero wind which signals the end of the heat wave leads to the formation of violent and intense thunderstorms with strong gusts and hail.[9][29][30] Occasionally, a tornado can form, which can strike the city although most tornadoes are relatively weak and rarely cause deaths.[31] The greatest risk for tornadoes occurs in the summer season due to the favourable conditions.[31] These severe storms can damage cars, houses and disrupt public services such as transportation and collection and disposal of urban solid waste.[32]:39

The highest temperature recorded in Buenos Aires is 43.3 °C (109.9 °F) on January 29, 1957.[1]

Autumn

At the beginning of the season, temperatures are hot in the afternoon while nights and mornings are mild.[33] Later on in the season, conditions are cooler featuring mild afternoons, and cold nights and mornings.[33] The average high and low are 22.8 °C (73.0 °F) and 13.5 °C (56.3 °F) respectively while precipitation averages 304.7 mm (12.00 in) during this season.[33] Similar to Spring, the season is characterized by changeable weather conditions with temperatures that can fluctuate;[20] temperatures as high as 37.9 °C (100.2 °F) and as low as −4.0 °C (24.8 °F) have been recorded.[33] Periods of rainy weather occur although these are usually of short duration.[6] Frosts rarely occur though they can occur as early as May.[34]

Winter

Snowfall in Buenos Aires
Picture showing snow covering Plaza de Mayo in 1918
Snow in Plaza de Mayo in 1918		 Snowfall in Buenos Aires in 2007
Snow in Buenos Aires in 2007

June to August are the winter months in Buenos Aires.[2] Winters are cold with mild temperatures during the day and cold nights.[6] July is the coldest month.[23] Highs during the season average 16.1 °C (61.0 °F) while lows average 7.9 °C (46.2 °F).[2] Lows rarely drop below 0 °C (32.0 °F), averaging 2 days each year at the central observatory,[34] and 1 day at Aeroparque.[35] Cold waves can occur in these months in which periods of cold temperatures can persist for days.[2] These cold waves, particularly during severe winters lead to increases in energy demand, which can cause significant energy shortages.[5] Snow occasionally occurs in the surrounding areas of the city but rarely within Buenos Aires proper; snow has only been observed twice on 9 July 2007 during a winter storm and in June 1918 since the start of meteorological observations in 1906 at the central observatory.[5] This is due to the city center having higher temperatures than the surrounding areas owing to the Urban heat island effect.[7]

Most of the precipitation comes from frontal systems associated with cyclogenesis and strong southeasterly winds) Sudestada, which bring long periods of precipitation, cloudy weather and cooler temperatures.[11][12][13] Winters are cloudy while relative humidity is very high, often 90% or higher, making the weather dull, grey and cool.[36] Towards the end of winter in August, there are important changes in the atmospheric circulation.[37] Warm, humid air penetrates the city, higher solar radiation and frequent synoptic weather disturbances from the west occur during the end of the winter.[37] As such, the end of winter is usually characterized by heavy storms with lightning.[37][38] This is popularly known as the Santa Rosa Storm, which occurs on August 30.[37][38] Based on 107 years of weather observations (1906–2012) from the central observatory, 58 years have seen stormy weather occurring on days close to August 30 although not all of these events have heavy precipitation.[37]

The lowest temperature recorded in Buenos Aires is −5.4 °C (22.3 °F) on July 9, 1918.[2]

Statistics

See also

Notes

  1. ↑ Station ID for Buenos Aires Observatorio is 87585 Use this station ID to locate the sunshine duration

References

  1. 1 2 3 4 5 6 "El Verano en la Ciudad de Buenos Aires" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  2. 1 2 3 4 5 "El Invierno en la Ciudad de Buenos Aires" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 24 December 2015.
  3. 1 2 3 4 5 "Clima" (in Spanish). Atlas Ambiental de Buenos Aires. Retrieved 24 December 2015.
  4. ↑ Peel, M. C. and Finlayson, B. L. and McMahon, T. A. (2007). "Updated world map of the Köppen−Geiger climate classification" (PDF). Hydrol. Earth Syst. Sci. 11: 1633–1644. doi:10.5194/hess-11-1633-2007. ISSN 1027-5606.
  5. 1 2 3 Pezza, Alexandre; Simmonds, Ian; Coelho, Caio (2010). "The unusual Buenos Aires snowfall of July 2007". Atmospheric Science Letters (John Wiley & Sons) 11 (4): 249–254. Bibcode:2010AtScL..11..249P. doi:10.1002/asl.283. Retrieved 25 September 2015.
  6. 1 2 3 4 5 6 "Clima" (in Spanish). Official Tourism site of Buenos Aires. Retrieved 24 December 2015.
  7. 1 2 "Capítulo 2: Impacto en la Ciudad de Buenos Aires" (PDF). Plan de Acción Buenos Aires 2030 (in Spanish). Gobierno de la Ciudad de Buenos Aires. Retrieved 29 December 2015.
  8. 1 2 3 4 5 Blouet 2010, p. 391.
  9. 1 2 3 4 "Viento Pampero" (in Spanish). Servicio Meteorológico Nacional. Retrieved 2 January 2016.
  10. ↑ Isla 2009, p. 57.
  11. 1 2 Biogeography and Ecology in South America 1969, p. 73.
  12. 1 2 The Physical Geography of South America 2007, p. 234.
  13. 1 2 3 "Sudestada" (in Spanish). Servicio Meteorológico Nacional. Retrieved 11 June 2015.
  14. 1 2 "Capítulo 7: Isla de calor urbana" (PDF). Plan de Acción Buenos Aires 2030 (in Spanish). Gobierno de la Ciudad de Buenos Aires. Retrieved 14 February 2016.
  15. 1 2 3 Figuerola, Patricia; Mazzeo, Nicolás (1998). "Urban-Rural Temperature Differences in Buenos Aires". International Journal of Climatology (John Wiley & Sons) 18 (15): 1709–1723. doi:10.1002/(SICI)1097-0088(199812)18:15<1709::AID-JOC338>3.0.CO;2-I. Retrieved 14 February 2016.
  16. ↑ Crop Stress Management 2011, p. 47.
  17. 1 2 3 Agricultural Prairies 2015, p. 151.
  18. 1 2 Crop Stress Management 2011, p. 48.
  19. 1 2 3 4 "La Primavera en la Ciudad de Buenos Aires" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 2 January 2016.
  20. 1 2 "Buenos Aires". Encyclopædia Britannica. Retrieved 3 January 2016.
  21. 1 2 "Temperaturas Invernales en Pleno Noviembre" (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  22. ↑ "Resumen Estadístico y Cronológico de las Olas de Calor en la Ciudad de Buenos Aires" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  23. 1 2 3 "Temperatura" (in Spanish). Atlas Ambiental de Buenos Aires. Retrieved 24 December 2015.
  24. ↑ "Climate Overview" (PDF). Met Office. Retrieved 7 June 2015.
  25. ↑ The Physical Geography of South America 2007, p. 233.
  26. ↑ Bronstein, Hugh (31 December 2013). "Analysis: Fernandez image wilts in year–end heat wave". Reuters. Retrieved 3 January 2016.
  27. 1 2 "Buenos Aires residents protest over 'heatwave power cuts'". BBC News. 31 December 2013. Retrieved 3 January 2016.
  28. ↑ "Informe Especial debido a la Ocurrencia de una Ola de Calor Excepcional en Argentina Durante Diciembre de 2013" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  29. 1 2 "El Pampero, Un Viento del Sur Indómito y Mañero" (PDF) (in Spanish). Retrieved 10 January 2016.
  30. ↑ Mezher, Romina; Doyle, Moira; Barros, Vicentre (2012). "Climatology of hail in Argentina". Atmospheric Research (Elsevier). 114–115 (1): 70–82. Bibcode:2012AtmRe.114...70M. doi:10.1016/j.atmosres.2012.05.020. Retrieved 19 September 2015.
  31. 1 2 "Tornados y tormentas eléctricas" (in Spanish). Ministerio de Salud. Retrieved 12 September 2015.
  32. ↑ "Chapter 2: Assessment of Disaster Risk Management Strategies in Argentina" (PDF). Improving the Assessment of Disaster Risks to Strengthen Financial Resilience. World Bank. Retrieved 9 September 2015.
  33. 1 2 3 4 "El Otoño en la Ciudad de Buenos Aires" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  34. 1 2 "Heladas Meteorológicas: Buenos Aires OBS.". Heladas en la Argentina (in Spanish). Facultad de Agronomía - Universidad de Buenos Aires. Retrieved 29 December 2015.
  35. ↑ "Heladas Meteorológicas: Aeroparque AERO". Heladas en la Argentina (in Spanish). Facultad de Agronomía - Universidad de Buenos Aires. Retrieved 29 December 2015.
  36. ↑ Lydolph 1985, p. 334.
  37. 1 2 3 4 5 "La Tormenta de Santa Rosa" (in Spanish). Servicio Meteorológico Nacional. Retrieved 2 January 2016.
  38. 1 2 "Geography and Climate of Argentina". Government of Argentina. Retrieved 28 August 2015.
  39. ↑ "Centenario de la Creación del Observatorio Central Buenos Aires, del Servicio Meteorológico Nacional" (PDF) (in Spanish). Servicio Meteorológico Nacional. Retrieved 11 January 2016.
  40. ↑ "Buenos Aires Climate Normals 1961–1990". National Oceanic and Atmospheric Administration. Retrieved 3 January 2016.
  41. ↑ "Station 87585 Buenos Aires Observatorio". Global station data 1961–1990—Sunshine Duration. Deutscher Wetterdienst. Retrieved 12 January 2016.
  42. 1 2 3 "Valores Medios de Temperature y Precipitación-Capital Federal: Buenos Aires" (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  43. ↑ "Caracteristicas Climaticas de la Ciudad de Buenos Aires" (in Spanish). Servicio Meteorológico Nacional. Retrieved 3 January 2016.
  44. ↑ "Aeroparque B. Aires Aero Climate Normals 1961–1990". National Oceanic and Atmospheric Administration. Retrieved 3 January 2016.
  45. ↑ "Ezeiza Aero Climate Normals 1961–1990". National Oceanic and Atmospheric Administration. Retrieved 11 January 2016.

Books

External links

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