Humid subtropical climate: Map

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Humid subtropical climate (Köppen Cfa or Cwa) is a climate zone characterized by hot, humid summers and cool winters. This climate type covers a broad category of climates, and the term "subtropical" may be a misnomer for the winter climate.

Significant amounts of precipitation occur in all seasons in most areas. 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.

Humid subtropical climates lie on the southeast side of all continents except Antarctica

, roughly between latitudes 25° and 40° north and south. Two of the few exceptions where this climate zone reaches up to latitude 46° north are in the Po Valley and the Toulouse

regions in Europe.

The Koppen definition of this climate is for the coldest month's mean temperature to be between and , and the warmest month to be above ; 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 per month or more than one third as much the wettest winter month).

Africa

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 Africa 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. For example Richards Bay

experiences a daily average minimum of 12°C and a daily average maximum of 23°C in the coldest month, and did not drop below 4°C in the thirty years of records from 1961. Rainfall is distributed throughout the year, but is heavier in summer, with a high of 172 mm for January and a low of 57 mm for June at Richards Bay

Asia

Humid subtropical climates in Asia differ from those in other continents, in that they generally have a pronounced dry winter even on the poleward boundary of this region, with most falling in the Cwa classification. They occupy extensive arcs of lowlands from northern Pakistan

circling the Himalayas

to China, South Coast of South Korea

and Japan (most of Honshū

, Kyūshū

and Shikoku

). Some major Asian cities in this climate zone include Kathmandu

, Chengdu

, Chongqing

, Shanghai, Nanjing

, Busan

, Kyoto and Tokyo

. Hong Kong

and Taipei

are on the equatorward boundary of this zone and Qingdao

is on the northern boundary.

In most of this region, there is very little precipiation during the winter, owing to the powerful anticyclonic winds from Siberia

. Only in those parts of coastal eastern China, between approximately the Yellow River

and the Pearl River

, is there sufficient winter rainfall to produce a Cfa climate; even in these areas, rainfall and streamflow show a very pronounced summer peak quite unlike other regions of this climate type. The only area where the winter rainfall equals the summer rain is on the "San-in" (Sea of Japan

) coast of Japan

, which during winter is effectively on the windward side of the westerlies. The winter rainfall 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. In the west, humid subtropical climate border on continental climates as altitude increases, or on winter-rainfall climates in Pakistan.

Humid zones in 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 (Middle East). 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 Cfa/Cfb (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 northeastern 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 2,560 millimetres per year in Batumi

(Georgia) falling throughout the year. This climate in northern Turkey and western Georgia is, again, a Cfa/Cfb (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

In North America, humid subtropical climates are almost exclusively the domain of the American South, including the following states: the eastern half of Texas

, Louisiana

, most of Arkansas

, Alabama

, Mississippi

, Tennessee

, Georgia

, Kentucky

, most of Florida

, and Virginia

excluding upland regions of the Appalachians

and southwestern West Virginia

though the climate in many of these states including Alabama, Georgia, Tennessee and Arkansas are subject to extremes. It also exists in the Mid-Atlantic, in low-lying or urban areas in Maryland

, Delaware

, southeastern Pennsylvania

, southern and central New Jersey

, Long Island

, the island of Manhattan

, and along the immediate coastline of southern Connecticut

. It can also be found in the Midwest, primarily in the southern portions of Missouri

, Illinois

, Indiana

, and Ohio

. The Mid-Atlantic and Midwestern areas included in this climate typically see snowfall during the winter, with occasional heavy storms. The classic example of a humid subtropical climate is the 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). Major cities typically included in this climate zone include: Houston

, Dallas

, Atlanta

, Evansville, Memphis

, Birmingham

, New Orleans

, Nashville

, Charlotte

, Baltimore

, Jacksonville

, Orlando

, Tampa

, Richmond

, Norfolk

, Tulsa

, Washington, D.C.

and Little Rock

. Major cities on the northern periphery of this zone include: St. Louis

, Louisville

, Cincinnati

, Philadelphia

and New York City

. The climates of Dallas

, San Antonio

and Oklahoma City

display a marked reduction in rainfall that suggests a shading into steppe climates to be found farther west, as in Lubbock, Texas

. There is some debate over whether the New York City

area (including Long Island

and Connecticut

) falls under this category; depending on source, they could fall either in Cfa or Dfa, though they usually fall under Cfa or humid subtropical due to their proximity to the Atlantic Ocean and the warming Gulf Stream current.

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 in areas which would otherwise be classified as tropical.

Characteristics and variants

The southernmost limits of this climate lie just north of South Florida

and around southern coastal Texas

. Areas farther south have a true tropical climate, with very warm weather year round and minimal temperature differences between seasons. By contrast, the northernmost limits of the humid subtropical region experience much greater seasonal variation, as they draw influence from the Atlantic Ocean and its bays, Delaware Bay

and Chesapeake Bay. Farther away from the Atlantic, it is found at the edge of the Blue Ridge Mountains, west to Louisville, Kentucky

, then roughly along the lower Ohio River through Paducah

, Kentucky to a line near Springfield, Missouri

. 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 falls once or twice a season and is usually three inches or less and occasional snow and ice storms are not unusual; however, most of the winter temperatures remain above or well above freezing with hardy plant growth. In the northern limits of this climate zone, however, cities such as Louisville

, Cincinnati

, Philadelphia

and New York City

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. 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 spring, 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, generally see a peak of precipitation in the spring, and a deep, drought-like nadir in mid-summer.

South America

Most of north-eastern Argentina

, Uruguay

, southern Brazil

, and eastern Paraguay

is Cfa.

The Cwa climate occurs in parts of tropical highlands of São Paulo

state, Minas Gerais

and near the Andean highland in northwestern Argentina

Australia

The humid subtropical climate dominates most of eastern Australia south from about Bundaberg, Queensland

down to about Bega

on the south coast of New South Wales

. It extends from the coast inland to about Dubbo

and the Warrumbungle and Nandewar

mountain ranges, where it grades into arid climates. In the Great Dividing Range

and to the south of about Bega, this climate type grades into warm temperate climates (Köppen Cfb) as at Guyra

and Katoomba

, in New South Wales.

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

.

Many of Australia's major cities are also in this climate zone, including Sydney

, Brisbane

, Gold Coast, Canberra

, Newcastle

and Wollongong

Variations in Australia

There is considerable 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) 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.

In the Darling Downs and further south, the summer rainfall maximum is less marked and by the time one reaches Dubbo, there are actually on average more rainy days in the winter months. Temperatures here display much greater seasonal variation, with summers being generally very hot with maxima of around 32 °C (90 °F) and frosts being common during dry winters: at Mitchell

the temperature has reached as low as -9.4 °C (15 °F).

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

Some areas of Europe, such as parts of northeastern inland of the Iberian Peninsula

, northern Italy, coastal Croatia

, coastal Slovenia

, much of Serbia

and Kosovo

, on the black sea coast, north-western Bulgaria

, parts of Romania

, southernmost Ukraine

, have summers too warm (>22°C in the warmest month) to qualify as oceanic, no freezing month, and enough summer precipitation to preclude their classification as Mediterranean. These narrow bands of climate are classified as humid sub-tropical Cfa.

In the Azores, some islands have this climate, with very amene 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 subtropical humid climate, as with Corvo Island