Humid subtropical climate

Humid subtropical climate zones of the world

  Cfa

  Cwa

A humid subtropical climate (Köppen climate classification Cfa or Cwa) is a climate zone characterized by hot, humid summers and mild to cool winters. Under the Köppen climate definition, this category of climate type covers a broad range of attributes, and the term "subtropical" may be a misnomer for locations along the outer ranges.

Description

The Köppen definition of this climate is for the coldest month's mean temperature to be between −3 °C (26.6 °F), although some climatologists prefer to use 0 °C (32 °F), and 18 °C (64.4 °F), and the warmest month to be above 22 °C (71.6 °F); along with either a dry winter- with less than one tenth of the precipitation of the wettest summer month- (Köppen: w) or without dry season (Köppen: f, winter months get more than one tenth of the precipitation of the wettest summer month, and summer months get at least 30 mm (1.2 in) per month or more than one third as much the wettest winter month).

Significant amounts of precipitation occur in all seasons in most areas, though in regions bordering on semi-arid climates (usually at the western margins), irregular droughts can be common and catastrophic to agriculture. Winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and an occasional tropical storm, hurricane or cyclone.This region is moist in the summer, can be very cold in winters.

Distribution

Humid subtropical climates lie on the southeast side of all continents, generally between latitudes 25° and 40° north and south. However, in Europe, it extends above latitude 45° N, covering regions such as the Po Valley of Italy, which includes Venice, the Toulouse region of France, and along the Black Sea coast. In East Asia, the influence of the Siberian anticyclone depresses winter temperatures, pushing the southern boundary of this regime to around China's Hainan Island, at latitude 20° N.

Africa

Durban
Climate chart (explanation)
J F M A M J J A S O N D     134     28 21     113     28 21     120     28 20     73     26 17     59     25 14     28     23 11     39     23 11     62     23 13     73     23 15     98     24 17     108     25 18     102     27 20 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: [2]
Imperial conversion J F M A M J J A S O N D     5.3     82 70     4.4     82 70     4.7     82 68     2.9     79 63     2.3     76 57     1.1     73 51     1.5     73 51     2.4     73 55     2.9     74 60     3.9     75 62     4.3     77 65     4     80 68 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

In Africa, the humid subtropical climates are found in two separate areas on the southern hemisphere of the continent. The Cwa climate is found in over a large portion of the interior of the Middle and Eastern African regions. This area includes; central Angola, northeastern Zimbabwe, the Niassa, Manica and Tete provinces of Mozambique, the southern Congo provinces, southwest Tanzania, and the majority of Malawi, and Zambia. Some lower portions of the Ethiopian Highlands also have this climate.

The Cfa climate covers a relatively small area of coastal KwaZulu-Natal and Eastern Cape provinces of South Africa, and is characterised by oceanic influences that give mild temperatures, especially in winter when temperatures do not drop as low as in many other regions within the humid subtropical category.

Asia

Locations in Asia with a humid subtropical climate differ from those in other continents in that they often have marked seasonal differences in precipitation, if not very dry winters.

East Asia

Tokyo
Climate chart (explanation)
J F M A M J J A S O N D     49     10 2     60     10 2     115     13 5     130     18 11     128     23 15     165     25 19     162     29 23     155     31 24     209     27 21     163     22 15     93     17 10     40     12 5 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: Japan Meteorological Agency
Imperial conversion J F M A M J J A S O N D     1.9     50 36     2.4     50 36     4.5     55 41     5.1     65 51     5     73 59     6.5     77 66     6.4     84 73     6.1     87 76     8.2     80 69     6.4     71 59     3.7     62 49     1.6     54 40 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

In East Asia, this type climate is found in northern Vietnam, the southeastern quarter of mainland China, the northern half of Taiwan, narrow areas along the coast of South Korea, and Japan (Kyushu, Shikoku, and most of Honshu). Cities on the equatorward boundary of this zone include Hong Kong and Taipei while Qingdao is on the northern boundary.

In most of this region, there is extremely limited precipitation during the winter, owing to the powerful anticyclonic winds from Siberia. Only in inland areas below the Yangtze River and coastal areas between approximately the Huai River and the beginning of the coast of Guangdong is there sufficient winter rainfall to produce a Cfa climate; even in these areas, rainfall and streamflow show a highly pronounced summer peak quite unlike other regions of this climate type. The only area where winter precipitation equals the summer rain is on the "San-in" (Sea of Japan), or western, coast of Japan, which during winter is on the windward side of the westerlies. The winter precipitation in these regions is usually produced by low-pressure systems off the east coast that develop in the onshore flow from the Siberian high. Summer rainfall comes from the East Asian Monsoon and from frequent typhoons. Annual rainfall is generally over 1,000 mm (40 inches), and in areas below the Himalayas can be much higher still.

South Asia

Humid subtropical climates can also be found in South Asia, primarily in northern India. However, the humid subtropical climates exhibited here differ markedly from humid subtropical climates in East Asia (and for that matter a good portion of the globe). Winters here are typically mild, dry and relatively short. They also tend to be foggy. Summers tend to be long and very hot, with high temperatures sometimes exceeding 40°C. They also tend to be extremely dry, complete with dust storms, traits usually associated with arid or semiarid climates. This is followed by the monsoons, where the region experiences heavy rain on almost a daily basis. Average high temperatures decreases during the monsoon season but the humidity increases. This results in hot and humid conditions, similar to summers in humid subtropical climates. Cities such as New Delhi, Lucknow and Kanpur exhibit this atypical version of the climate. Islamabad also features this weather pattern, but with wetter winters.

In South Asia, humid subtropical climates generally border on continental climates as altitude increases, or on winter-rainfall climates in Pakistan.

Southwestern Asia (Northern Middle East and Caucasus)

Although humid subtropical climates in Asia are mostly confined to the southeastern quarter of the continent, there are areas on the Caspian Sea and Black Sea with humid subtropical climates that are unusually warm for their high latitudes and also unusual for this climate type, that snowfall in winter is relatively common, but is usually of a short duration.

In the narrow Caspian coastal strip of Iran (Gilan and Mazandaran) a humid subtropical climate prevails at an unusually high latitude. Annual rainfall ranges from around 740 mm (29 inches) at Sari to over 2,000 mm (78 inches) at Bandar-e Anzali, and is heavy throughout the year, with a maximum in October or November when Bandar-e Anzali can average 400 millimetres (16 inches). Temperatures are generally moderate in comparison with other parts of Southwestern Asia. In Rasht, the average maximum in July is around 28 °C (82 °F) but with near-saturation humidity, whilst in January it is around 9 °C (48 °F). The heavy, evenly distributed rainfall extends north into the Caspian coastal strip of Azerbaijan up to its northern border but this climate in Azerbaijan is, however, a Cfb/Cfa (Oceanic climate/Humid subtropical climate) borderline case. During winter, the coastal areas can receive snowfall, but is usually of a short duration. Annual rainfall in Lankaran in the southeast averages up to 1,800 mm (70 inches) and is heavy throughout the year; and annual rainfall is generally over 1,000 mm (40 inches) in the foothills of the Caucasus in the northeast, as altitude increases and the humid subtropical climate changes to the oceanic climate

Western Georgia in the Kolkheti Lowland and the north coast of Turkey, have a climate similar to that of Gilan and Mazandaran in Iran and very similar to that of southeastern and northern Azerbaijan. Temperatures range from 22 °C in summer to 5 °C in winter and rainfall is even heavier than in Caspian Iran, up to 2,300 millimetres per year in Hopa (Turkey) and up to 2,718 millimetres per year in Batumi (Georgia) falling throughout the year. This climate in northern Turkey and western Georgia is, again, a Cfb/Cfa (Oceanic climate/Humid subtropical climate) borderline case. And again, during winter, the coastal areas can receive snowfall, but is usually of a short duration.

North America

Climate Zones of the Continental United States

In North America, humid subtropical climates are almost exclusively the domain of the American South, including the following states: the eastern half of Texas, Oklahoma, Louisiana, Arkansas, Alabama, Mississippi, North Carolina, South Carolina, Tennessee, Georgia, Kentucky, most of Florida, Virginia, and southern West Virginia. The climate in many of these states is subject to extremes. The humid subtropical climate can also be found in the Midwest, primarily in the central and southern portions of Kansas, Missouri, Illinois, Indiana and Ohio. It can also be found in the Mid-Atlantic, primarily Maryland, Delaware, the District of Columbia, southeastern Pennsylvania, southern New Jersey, far southern New York, specifically New York City and coastal Connecticut. The Mid-Atlantic and Midwestern areas included in this climate typically see snowfall during the winter, with occasional heavy storms. The archetypal humid subtropical climate is best exemplified by the American Deep South, because the summers are long and almost tropical, and temperatures reach freezing only a few times in the winter with rare snowfall, usually three inches or less. Summers in this zone are hot and humid, with daily averages above 25 °C (77 °F).

In Mexico, there are small areas of Cfa and Cwa climates. They are both caused by the high elevations of Trans-Mexican Volcanic Belt and Sierra Madre Oriental. Despite being located at higher elevations, these locations have summers that are too warm to qualify as a subtropical highland climate. Guadalajara’s climate is a major example of this.

Characteristics and variants

Atlanta
Climate chart (explanation)
J F M A M J J A S O N D     128     11 1     119     14 3     137     18 6     92     23 10     100     27 15     92     30 20     130     32 21     93     31 21     104     28 18     79     23 12     104     17 6     97     13 2 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: NCDC
Imperial conversion J F M A M J J A S O N D     5     52 33     4.7     57 37     5.4     65 44     3.6     73 50     3.9     80 60     3.6     87 67     5.1     89 71     3.7     88 70     4.1     82 64     3.1     73 53     4.1     63 44     3.8     55 36 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Outside of the isolated higher-altitude sections of Mexico, the southernmost limits of this climate in North America lie just north of South Florida and around southern coastal Texas. Cities at the southernmost limits of this climate, such as Orlando and Tampa generally feature warm weather year round and minimal temperature differences between seasons. These cities fall just short of having a true tropical climate. In contrast, cities at the northernmost limits of the humid subtropical region, such as New York City, Philadelphia, and Louisville, Kentucky experience much greater seasonal variation. These cities generally feature hot, humid summers and cold winters. Areas farther north than this, inland, or at a higher elevation, fall into the humid continental climate category with harsher winters.

Snowfall varies greatly in this climate zone. In locations at the southern limits of this zone and areas around the Gulf Coast, cities such as Orlando, Tampa, Houston, and New Orleans rarely see snowfall, which occurs, at most, a few times per generation. In inland southern cities farther north, such as Atlanta, Memphis, Little Rock, Nashville, Dallas, Charlotte, and Raleigh, snow typically falls once or twice a season and is usually three inches or less. Ice storms are not unusual at these locations. However for the majority of the winter here, temperatures remain above or well above freezing, with slight plant growth. In the northern limits of this climate zone, places such as Philadelphia, New York City and coastal Connecticut experience snow every winter, sometimes accumulating heavily although it melts more quickly than in regions to the north.

Precipitation is plentiful in the humid subtropical climate zone in North America. Although most areas tend to have precipitation spread evenly throughout the year, a somewhat monsoon-like pattern is seen in parts of the Southeast (in locales such as Augusta, Georgia and Columbia, South Carolina), which experience dry winters (by humid subtropical standards) and warm springs, followed immediately by a long, hot, rainy and humid summer. In addition, areas in Texas that are slightly inland from the Gulf of Mexico, such as Austin and San Antonio that border the semi-arid climate zone, generally see a peak of precipitation in the spring, and a deep, drought-like nadir in mid-summer.

South America

Buenos Aires
Climate chart (explanation)
J F M A M J J A S O N D     122     30 20     123     29 19     154     26 17     107     23 14     92     19 10     50     16 8     53     14 7     63     17 9     78     19 10     139     23 13     131     25 16     103     28 18 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: National Meteorological Service
Imperial conversion J F M A M J J A S O N D     4.8     87 69     4.8     84 67     6.1     80 63     4.2     73 57     3.6     66 51     2     60 46     2.1     57 45     2.5     63 48     3.1     66 50     5.5     73 55     5.2     78 61     4.1     83 65 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Humid subtropical climates are found in a sizeable portion of South America. Most of north-eastern Argentina, Uruguay, southern Brazil, and eastern Paraguay features this climate. Major cities such as São Paulo, Buenos Aires, Porto Alegre and Montevideo. have a humid subtropical climate, generally in the form of hot humid summers and mild to cool winters. These areas, which include the Pampas, generally feature a Cfa climate categorization.

The Cwa climate occurs in parts of tropical highlands of São Paulo state, Minas Gerais and near the Andean highland in northwestern Argentina. These highland areas feature summer temperatures that are warm enough to fall outside the subtropical highland climate category.

Australia

Brisbane
Climate chart (explanation)
J F M A M J J A S O N D     154     30 21     161     30 21     139     29 20     91     27 17     78     25 14     69     22 12     54     22 10     44     23 11     44     26 14     78     27 16     99     28 19     130     29 20 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source:
Imperial conversion J F M A M J J A S O N D     6.1     86 70     6.3     86 70     5.5     84 68     3.6     81 63     3.1     77 57     2.7     72 54     2.1     72 50     1.7     73 52     1.7     79 57     3.1     81 61     3.9     82 66     5.1     84 68 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

The humid subtropical climate dominates half of eastern Australia.

This zone contains the only regions where soils are not acutely deficient in phosphorus, as well as the heaviest rainfall south of the Tropic of Capricorn, making it prime agricultural country, centred on towns such as Coffs Harbour, Grafton, Kempsey, Port Macquarie, Tamworth, and Moree.

Variations in Australia

There is variation in climate within this zone. Annual rainfall on the coast can reach as high as 2,000 mm (80 inches) in favourable locations and is generally above 1,000 mm (40 inches). However, because most of the heaviest two- and three-day rainfalls in the world occur in this coastal zone as a result of east coast lows forming to the north of a large high pressure system, there can be great variation in rainfall from year to year. At Lismore in the centre of this zone, the annual rainfall can range from less than 550 mm (22 inches) in 1915 to more than 2,780 mm (110 inches) in 1950. There is usually a distinct summer rainfall maximum that becomes more pronounced moving northwards: in Brisbane the wettest month (February) receives five times the rainfall of the driest (September). Temperatures are very warm to hot but not excessive: the average maximum in February is usually around 29 °C (84 °F) and in July around 21 °C (70 °F). Frosts are extremely rare except at higher elevations, but temperatures over 35˚C (95˚F) are not common on the coast.

North of the Cfa climate zone there is a zone centred upon Rockhampton and extending up to the Atherton Tableland of Köppen Cwa climate. This has a very pronounced dry winter with often negligible rainfall between June and October, and winter temperatures generally only slightly below 18°C, above which one would have a tropical savanna, or Aw, climate.

Europe

Humid subtropical climates are found in only small sections of Europe, not nearly as widespread as it is on the other aforementioned continents. Some areas of Europe, such as parts of the northeastern interior of the Iberian Peninsula, parts of inland and Adriatic northern Italy, parts of Epirus in Greece around the area of Ioannina, parts of coastal northern Croatia, coastal Slovenia, the Black Sea coast of Bulgaria, Romania, Sochi, Russia and southernmost Ukraine have summers too warm (>22°C in the warmest month) to qualify as oceanic, no freezing month, and enough summer precipitation and sometimes humid conditions to preclude their classification as Mediterranean. In the Azores, some islands have this climate, with very mild and rainy winters (> 13°C), hot summers (> 22 or 23°C) but with no dry season during the warmest period, which means that they can be classified neither as oceanic, nor as Mediterranean, but only as humid subtropical climate, as with Corvo Island.

See also

• Subtropics
• Subtropical ridge
• Köppen climate classification