Humid subtropical climates are characterized by hot, humid summers and cool to mild winters. Rainfall is distributed fairly evenly throughout the year. Winter rainfall—and sometimes snowfall—is associated with large storm systems that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and an occasional tropical storm or hurricane. Humid subtropical climates lie on the southeast side of continents, roughly between 25 degrees and 37 degrees latitude. The main temperature range in this climate, considering normal annual extremes, is 20° F to 110 °F (-5°C to 38°C), though this range may greatly depending on the exact location.

Humid subtropical climates in Asia

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Humid subtropical climates are found on the east-central coast of China, as well as in the majority of South Korea and lowland Japan. However, the distinction is difficult to make in Japan, whose temperatures can either be considered subtropical or humid continental, depending on latitude.

Humid subtropical climates in North America

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In North America, humid subtropical climates are almost exclusively the domain of the American South, including part or most of eastern Texas, Louisiana, most of Arkansas, Mississippi, parts of Tennessee, Alabama, North Carolina, Georgia, Virginia, northern and central portions of Florida, South Carolina, and eastern portions of Maryland. The exceptions in those states lie in the higher elevations, particularly in the Appalachian Mountains, where a humid continental climate exists due to the higher elevation and colder overall temperatures (especially in the winter).

Major cities in this climate zone include Atlanta, Georgia, Houston, Texas, New Orleans, Louisiana, Nashville, Tennessee, Charlotte, North Carolina, Raleigh, North Carolina, Washington, D.C., and Baltimore, Maryland.

Characteristics and variants

The northernmost limit of the humid subtropical climate is often considered to be Baltimore, Maryland. Areas of the state further inland tend towards a more humid continental climate; it appears that the foothills of the Appalachian Mountains to the north and west of Baltimore may protect the city from harsh Canadian winds during the winter. In addition, the moderating effect of the Chesapeake Bay and Atlantic Ocean may also play a part in Baltimore's relatively mild climate.

Snowfall is a rarity in this climate zone, with significant amounts, along with accumulation of ice, occurring mainly in the Baltimore/DC area, and in Nashville and Atlanta. Snowfall is commonplace to the west at the higher elevations (>1000 m, >3100 ft.) though in the Appalachian Mountains as far south as Georgia.

Although most areas with humid subtropical climates tend to have precipitation spread evenly throughout the year, a somewhat monsoon-like pattern is seen in parts of the extreme Southeast (in locales such as Augusta, Georgia and Columbia, South Carolina), which experience an extremely dry (by humid subtropical standards) and warm spring, followed immediately by a hot 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.

Climate