A humid subtropical climate (Köppen climate classification Cfa or Cwa) is a zone of subtropical climate characterised by hot, usually humid summers and mild to cool winters. Under the Köppen climate definition, this category of climate type covers a broad range of attributes, especially in terms of winter temperatures. Under the modern Trewartha climate classification, most of the climates that have eight or more months with a mean temperature of 10 °C (50 °F) are warm to hot much of the year with mild winters.