A humid subtropical climate is characterized by hot, humid summers and mild, chilly winters. This climate type is normally found on the eastern sides of continents between 20° and 35° north and south of the equator. Most humid subtropical climates are found along the coast due to the influence of moist maritime air, but may also extend inland for quite some distance (as is the case in North America and China).
Defined under the 1966 Trewartha update to the Koppen climate classification system, humid subtropical climates have a monthly mean air temperature higher than 10 °C (50 °F) for eight or more months a year and at least one month with mean temperature below 18 °C (64.4 °F). The influence of very cold air masses from the polar front can result in occasional frosts and tornadoes in the southeastern United states, while the influence of the monsoon system is felt in east and south Asia. Rainfall is more or less evenly distributed throughout the year. Annual precipitation varies from 254 cm (100 in) near the coast to 63.5 cm (25 in) inland.
Humid subtropical climates can be found in the southeastern United States, southeastern South America, coastal southeast South Africa, eastern Australia and eastern Asia from northern India through south China to Japan.
Soil Health Challenges for Humid Subtropical Climates
Belda, M., Holtanová, E., Halenka, T., & Kalvová, J. (2014). Climate classification revisited: from Köppen to Trewartha. Climate research, 59(1), 1-13.