<P> Under the Köppen climate classification, Cfa and Cwa climates are either described as humid subtropical climates or mild temperate climates . This climate features mean temperatures in the coldest month between 0 ° C (32 ° F) and 18 ° C (64 ° F) and mean temperatures in the warmest month 22 ° C (72 ° F) or higher . However, while some climatologists have opted to describe this climate type as a "humid subtropical climate", Köppen himself never used this term . The humid subtropical climate classification was officially created under the Trewartha Climate classification . </P> <P> The Trewartha system was a 1966 update of the Köppen climate classification, and sought to redefine middle latitude climates into smaller zones (the original Köppen system grouped all middle latitude climates into a single zone). Under the Trewartha climate classification, climates are termed humid subtropical when they have monthly mean air temperatures 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). Under the Trewartha system, humid subtropical climates typically occupy the southernmost portions of the temperate zone from 23.5 to 35.0 north and south latitude . </P> <P> Rainfall often shows a summer peak, especially where monsoons are well developed, as in Southeast Asia and Florida (US). Other areas have a more uniform or varying rainfall cycles, but consistently lack any predictably dry summer months . Most summer rainfall occurs during thunderstorms that build up due to the intense surface heating and strong subtropical sun angle . Weak tropical lows that move in from adjacent warm tropical oceans, as well as infrequent tropical storms often contribute to summer seasonal rainfall peaks . Winter rainfall is often associated with large storms in the westerlies that have fronts that reach down into subtropical latitudes . However, many subtropical climates such as southeast Asia or Florida have very dry winters, with frequent brush fires and water shortages . </P> <Table> <Tr> <Th> Durban, South Africa </Th> </Tr> <Tr> <Th> Climate chart (explanation) </Th> </Tr> <Tr> <Td> <Table> <Tr> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> J </Td> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> O </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 134 28 21 </Td> <Td> 113 28 21 </Td> <Td> 120 28 20 </Td> <Td> 73 26 17 </Td> <Td> 59 25 14 </Td> <Td> 38 23 11 </Td> <Td> 39 23 11 </Td> <Td> 62 23 13 </Td> <Td> 73 23 15 </Td> <Td> 98 24 17 </Td> <Td> 108 25 18 </Td> <Td> 102 27 20 </Td> </Tr> <Tr> <Td_colspan="12"> Average max. and min . temperatures in ° C </Td> </Tr> <Tr> <Td_colspan="12"> Precipitation totals in mm </Td> </Tr> <Tr> <Td_colspan="12"> Source: </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td> <Table> <Tr> <Th_colspan="12"> (show) Imperial conversion </Th> </Tr> <Tr> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> J </Td> <Td> J </Td> <Td> </Td> <Td> </Td> <Td> O </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> 5.3 82 70 </Td> <Td> 4.4 82 70 </Td> <Td> 4.7 82 68 </Td> <Td> 2.9 79 63 </Td> <Td> 2.3 76 57 </Td> <Td> 1.5 73 51 </Td> <Td> 1.5 73 51 </Td> <Td> 2.4 73 55 </Td> <Td> 2.9 74 60 </Td> <Td> 3.9 75 62 </Td> <Td> 4.3 77 65 </Td> <Td> 80 68 </Td> </Tr> <Tr> <Td_colspan="12"> Average max. and min . temperatures in ° F </Td> </Tr> <Tr> <Td_colspan="12"> Precipitation totals in inches </Td> </Tr> </Table> </Td> </Tr> </Table>

The dominant source of precipitation in the moist subtropical climate is